<PAGE>   1

     As filed with the Securities and Exchange Commission on June 22, 2000
                                                   Registration No. 333-________


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      Under
                           The Securities Act of 1933

                                   COM21, INC.
             (Exact name of registrant as specified in its charter)

             DELAWARE                                    94-3201698
  (State or other jurisdiction              (IRS Employer Identification No.)
of incorporation or organization)

                                750 TASMAN DRIVE
                           MILPITAS, CALIFORNIA 95035
               (Address of principal executive offices) (Zip Code)

                                   COM21, INC.
                            1998 STOCK INCENTIVE PLAN
                        1998 EMPLOYEE STOCK PURCHASE PLAN
                             2000 STOCK OPTION PLAN
                            (Full title of the Plans)

                                 PETER D. FENNER
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                   COM21, INC.
                                750 TASMAN DRIVE
                           MILPITAS, CALIFORNIA 95035
                     (Name and address of Agent for service)
                                 (408) 953-9100
          (Telephone number, including area code, of agent for service)

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                                         Proposed           Proposed
         Title of                                                        Maximum            Maximum
        Securities                             Amount                    Offering           Aggregate               Amount of
           to be                               to be                      Price             Offering               Registration
        Registered                          Registered(1)              per Share(2)          Price(2)                  Fee
        ----------                        ---------------              ------------         ---------              ------------
<S>                                       <C>                          <C>                  <C>                    <C>
1998 Stock Incentive Plan
Common Stock, $0.001 par value            3,015,237 shares             $23.75              $ 71,611,878.75         $ 18,905.54


1998 Employee Stock Purchase Plan
Common Stock, $0.001 par value              450,000 shares             $23.75              $ 10,687,500.00         $  2,821.50


2000 Stock Option Plan
Common Stock, $0.001 par value            1,500,000 shares             $23.75              $356,250,000.00         $ 94,050.00

                                                                                             Aggregate Filing Fee: $115,777.04
</TABLE>


(1)  This Registration Statement shall also cover any additional shares of
     Common Stock which become issuable under the Com21, Inc. 1998 Stock
     Incentive Plan, 1998 Employee Stock Purchase Plan and/or 2000 Stock Option
     Plan by reason of any stock dividend, stock split, recapitalization or
     other similar transaction effected without the Registrant's receipt of
     consideration which results in an increase in the number of the outstanding
     shares of the Registrant's Common Stock.

(2)  Calculated solely for purposes of this offering under Rule 457(h) of the
     Securities Act of 1933, as amended (the "1933 Act"), on the basis of the
     average of the high and low selling prices per share of Registrant's Common
     Stock on June 19, 2000, as reported on the Nasdaq National Market.


<PAGE>   2


                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT



Item 3. Incorporation of Documents by Reference

        Com21, Inc. (the "Registrant") hereby incorporates by reference into
this Registration Statement the following documents previously filed with the
Securities and Exchange Commission (the "Commission"):

        (a) The Registrant's Annual Report on Form 10-K for the fiscal year
            ended December 31, 1999 filed with the Commission on March 24, 2000,
            pursuant to Section 13 of the Securities Exchange Act of 1934 , as
            amended (the "1934 Act");

        (b) The Registrant's Current Report on Form 8-K for period date April
            18, 2000 filed with the commission on April 24, 2000;

        (c) The Registrant's Quarterly Report on Form 10-Q for the fiscal
            quarter ended March 31, 2000 filed with the Commission on May 15,
            2000; and

        (d) The Registrant's Registration Statement No. 000-24009 on Form 8-A
            filed with the Commission on April 8, 1998, pursuant to Section
            12(b) of the 1934 Act in which there is described the terms, rights
            and provisions applicable to the Registrant's outstanding Common
            Stock.

        All reports and definitive proxy or information statements filed
pursuant to Section 13(a), 13(c), 14 or 15(d) of the 1934 Act after the date of
this Registration Statement and prior to the filing of a post-effective
amendment which indicates that all securities offered hereby have been sold or
which de-registers all securities then remaining unsold shall be deemed to be
incorporated by reference into this Registration Statement and to be a part
hereof from the date of filing of such documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference herein shall be
deemed to be modified or superseded for purposes of this Registration Statement
to the extent that a statement contained herein or in any subsequently filed
document which also is deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

Item 4. Description of Securities

        Not Applicable.

Item 5. Interests of Named Experts and Counsel

        Not Applicable.

Item 6. Indemnification of Directors and Officers

        The Registrant's Certificate of Incorporation limits the liability of
directors to the maximum extent permitted by Delaware law. Delaware law provides
that directors of a corporation will not be personally liable for monetary
damages for breach of their fiduciary duties as directors, except for liability
for (i) any breach of their duty of loyalty to the corporation or its
stockholders, (ii) acts or omissions not in good faith or that involve
intentional misconduct or a knowing violation of law, (iii) unlawful payments of
dividends or unlawful stock repurchases or redemptions as provided in Section
174 of the Delaware General Corporation Law, or (iv) any transaction from which
the director derives an improper personal benefit.

        The Registrant's Bylaws provide that the Registrant shall indemnify its
directors and may indemnify its officers, employees and other agents to the
fullest extent permitted by law. The Registrant believes that indemnification
under its Bylaws covers at least negligence and gross negligence on the part of
an indemnified party in connection with the defense of any action or proceeding
arising out of such party's status or service as a director, officer, employee
or other agent of the Company upon an undertaking by such party to repay such
advances if it is ultimately determined that such party is not entitled to
indemnification. The Registrant has entered into


                                      II-1
<PAGE>   3

Indemnification Agreements with its officers and directors. The Indemnification
Agreements provide the Registrant's officers and directors with further
indemnification to the maximum extent permitted by the Delaware General
Corporation Law.

Item 7. Exemption from Registration Claimed

        Not Applicable.

Item 8. Exhibits

<TABLE>
<CAPTION>
Exhibit Number      Exhibit
--------------      -------
<S>                 <C>
     4.0            Instruments Defining Rights of Stockholders. Reference is
                    made to the Registrant's Registration Statement No.
                    000-24009 on Form 8-A and the exhibits thereto, which are
                    incorporated herein by reference pursuant to Item 3(d) of
                    this Registration Statement.

     5.0            Opinion of Brobeck, Phleger & Harrison LLP.

    23.1            Consent of Independent Auditors

    23.2            Consent of Brobeck, Phleger & Harrison LLP is contained in
                    Exhibit 5.

    24.0            Power of Attorney. Reference is made to page II-3 of this
                    Registration Statement.

    99.1            Com21, Inc. 1998 Stock Incentive Plan (Amended and Restated
                    As of March 1999).

    99.2            Com21, Inc. 1998 Employee Stock Purchase Plan (Amended and
                    Restated as of January 12, 2000).

    99.3            Com21, Inc. 2000 Stock Option Plan.
</TABLE>

Item 9. Undertakings

        A. The undersigned Registrant hereby undertakes: (1) to file, during any
period in which offers or sales are being made, a post-effective amendment to
this Registration Statement (i) to include any prospectus required by Section
10(a)(3) of the 1933 Act, (ii) to reflect in the prospectus any facts or events
arising after the effective date of this Registration Statement (or the most
recent post-effective amendment thereof) which, individually or in the
aggregate, represent a fundamental change in the information set forth in this
Registration Statement and (iii) to include any material information with
respect to the plan of distribution not previously disclosed in this
Registration Statement or any material change to such information in this
Registration Statement; provided, however, that clauses (1)(i) and (1)(ii) shall
not apply if the information required to be included in a post-effective
amendment by those clauses is contained in periodic reports filed by the
Registrant pursuant to Section 13 or Section 15(d) of the 1934 Act that are
incorporated by reference into this Registration Statement; (2) that for the
purpose of determining any liability under the 1933 Act each such post-effective
amendment shall be deemed to be a new registration statement relating to the
securities offered therein and the offering of such securities at that time
shall be deemed to be the initial bona fide offering thereof; and (3) to remove
from registration by means of a post-effective amendment any of the securities
being registered which remain unsold at the termination of the Registrant's 1998
Stock Incentive Plan, 1998 Employee Stock Purchase Plan and/or 2000 Stock Option
Plan.

        B. The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the 1933 Act, each filing of the Registrant's
annual report pursuant to Section 13(a) or Section 15(d) of the 1934 Act that is
incorporated by reference into this Registration Statement shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

        C. Insofar as indemnification for liabilities arising under the 1933 Act
may be permitted to directors, officers or controlling persons of the Registrant
pursuant to the indemnification provisions summarized in Item 6 or otherwise,
the Registrant has been advised that, in the opinion of the Commission, such
indemnification is against public policy as expressed in the 1933 Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer, or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the 1933 Act and will be governed by the final
adjudication of such issue.


                                      II-2
<PAGE>   4

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8, and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Milpitas, State of California on 9th day of
June, 2000.

                                            COM21, INC.


                                            By: /s/ Peter D. Fenner
                                               ---------------------------------
                                               Peter D. Fenner
                                               President, Chief Executive
                                               Officer and Director



                                POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS:

        That the undersigned officers and directors of Com21, Inc., a Delaware
corporation, do hereby constitute and appoint Peter D. Fenner and David L.
Robertson and each of them, the lawful attorneys-in-fact and agents with full
power and authority to do any and all acts and things and to execute any and all
instruments which said attorneys and agents, and any one of them, determine may
be necessary or advisable or required to enable said corporation to comply with
the Securities Act of 1933, as amended, and any rules or regulations or
requirements of the Securities and Exchange Commission in connection with this
Registration Statement. Without limiting the generality of the foregoing power
and authority, the powers granted include the power and authority to sign the
names of the undersigned officers and directors in the capacities indicated
below to this Registration Statement, to any and all amendments, both
pre-effective and post-effective, and supplements to this Registration
Statement, and to any and all instruments or documents filed as part of or in
conjunction with this Registration Statement or amendments or supplements
thereof, and each of the undersigned hereby ratifies and confirms that all said
attorneys and agents, or any one of them, shall do or cause to be done by virtue
hereof. This Power of Attorney may be signed in several counterparts.

        IN WITNESS WHEREOF, each of the undersigned has executed this Power of
Attorney as of the date indicated.

        Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.

<TABLE>
<CAPTION>
Signature                      Title                                            Date
---------                      -----                                            ----
<S>                            <C>                                              <C>
/s/ Peter D. Fenner            President, Chief Executive Officer and           June 9, 2000
------------------------       Director (Principal Executive Officer)
Peter D. Fenner


/s/ David L. Robertson         Chief Financial Officer, Vice President,         June 22, 2000
------------------------       Finance and Administration, Corporate
David L. Robertson             Secretary (Principal Financial Officer)


/s/ Paul Baran                 Chairman of the Board of Directors               June 22, 2000
------------------------
Paul Baran
</TABLE>


                                      II-3
<PAGE>   5

<TABLE>
<S>                            <C>                                              <C>
/s/ C. Richard Kramlich        Director                                         June 22, 2000
-----------------------
C. Richard Kramlich


/s/ Robert C. Hawk             Director                                         June 22, 2000
-----------------------
Robert C. Hawk


                               Director
-----------------------
Jerald L. Kent


/s/ Daniel J. Pike             Director                                         June 22, 2000
-----------------------
Daniel J. Pike


/s/ Robert W. Wilmot           Director                                         June 22, 2000
-----------------------
Robert W. Wilmot


                               Director
-----------------------
James J. Spilker, Jr.
</TABLE>


                                      II-4
<PAGE>   6


EXHIBIT INDEX


<TABLE>
<CAPTION>
Exhibit Number      Exhibit
--------------      -------
<S>                 <C>
     4.0            Instruments Defining Rights of Stockholders. Reference is
                    made to the Registrant's Registration Statement No.
                    000-24009 on Form 8-A and the exhibits thereto, which are
                    incorporated herein by reference pursuant to Item 3(d) of
                    this Registration Statement.

     5.0            Opinion of Brobeck, Phleger & Harrison LLP.

    23.1            Consent of Independent Auditors

    23.2            Consent of Brobeck, Phleger & Harrison LLP is contained in
                    Exhibit 5.

    24.0            Power of Attorney. Reference is made to page II-3 of this
                    Registration Statement.

    99.1            Com21, Inc. 1998 Stock Incentive Plan (Amended and Restated
                    as of March 1999).

    99.2            Com21, Inc. 1998 Employee Stock Purchase Plan (Amended and
                    Restated as of January 12, 2000).

    99.3            Com21, Inc. 2000 Stock Option Plan.
</TABLE>
[{"type": "S-8", "sequence": "1", "filename": "0001.txt", "description": "FORM S-8", "secsgml_size_bytes": 18407}]
{"company-data": {"conformed-name": "COM21 INC", "cik": "0000945379", "assigned-sic": "7370", "irs-number": "943201698", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-39898", "film-number": "659299"}, "business-address": {"street1": "750 MILPITAS DRIVE", "city": "MILPITAS", "state": "CA", "zip": "95035", "phone": "4089539100"}, "mail-address": {"street1": "750 MILPITAS DRIVE", "city": "MILPITAS", "state": "CA", "zip": "95035"}}
1

     As filed with the Securities and Exchange Commission on June 22, 2000
                                                   Registration No. 333-________

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      Under
                           The Securities Act of 1933

                                   COM21, INC.
             (Exact name of registrant as specified in its charter)

             DELAWARE                                    94-3201698
  (State or other jurisdiction              (IRS Employer Identification No.)
of incorporation or organization)

                                750 TASMAN DRIVE
                           MILPITAS, CALIFORNIA 95035
               (Address of principal executive offices) (Zip Code)

                                   COM21, INC.
                            1998 STOCK INCENTIVE PLAN
                        1998 EMPLOYEE STOCK PURCHASE PLAN
                             2000 STOCK OPTION PLAN
                            (Full title of the Plans)

                                 PETER D. FENNER
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                   COM21, INC.
                                750 TASMAN DRIVE
                           MILPITAS, CALIFORNIA 95035
                     (Name and address of Agent for service)
                                 (408) 953-9100
          (Telephone number, including area code, of agent for service)

                         CALCULATION OF REGISTRATION FEE
Proposed           Proposed
         Title of                                                        Maximum            Maximum
        Securities                             Amount                    Offering           Aggregate               Amount of
           to be                               to be                      Price             Offering               Registration
        Registered                          Registered(1)              per Share(2)          Price(2)                  Fee
        ----------                        ---------------              ------------         ---------              ------------
1998 Stock Incentive Plan
Common Stock, $0.001 par value            3,015,237 shares             $23.75              $ 71,611,878.75         $ 18,905.54

1998 Employee Stock Purchase Plan
Common Stock, $0.001 par value              450,000 shares             $23.75              $ 10,687,500.00         $  2,821.50

2000 Stock Option Plan
Common Stock, $0.001 par value            1,500,000 shares             $23.75              $356,250,000.00         $ 94,050.00

                                                                                             Aggregate Filing Fee: $115,777.04
(1)  This Registration Statement shall also cover any additional shares of
     Common Stock which become issuable under the Com21, Inc. 1998 Stock
     Incentive Plan, 1998 Employee Stock Purchase Plan and/or 2000 Stock Option
     Plan by reason of any stock dividend, stock split, recapitalization or
     other similar transaction effected without the Registrant's receipt of
     consideration which results in an increase in the number of the outstanding
     shares of the Registrant's Common Stock.

(2)  Calculated solely for purposes of this offering under Rule 457(h) of the
     Securities Act of 1933, as amended (the "1933 Act"), on the basis of the
     average of the high and low selling prices per share of Registrant's Common
     Stock on June 19, 2000, as reported on the Nasdaq National Market.
2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

        Com21, Inc. (the "Registrant") hereby incorporates by reference into
this Registration Statement the following documents previously filed with the
Securities and Exchange Commission (the "Commission"):

        (a) The Registrant's Annual Report on Form 10-K for the fiscal year
            ended December 31, 1999 filed with the Commission on March 24, 2000,
            pursuant to Section 13 of the Securities Exchange Act of 1934 , as
            amended (the "1934 Act");

        (b) The Registrant's Current Report on Form 8-K for period date April
            18, 2000 filed with the commission on April 24, 2000;

        (c) The Registrant's Quarterly Report on Form 10-Q for the fiscal
            quarter ended March 31, 2000 filed with the Commission on May 15,
            2000; and

        (d) The Registrant's Registration Statement No. 000-24009 on Form 8-A
            filed with the Commission on April 8, 1998, pursuant to Section
            12(b) of the 1934 Act in which there is described the terms, rights
            and provisions applicable to the Registrant's outstanding Common
            Stock.

        All reports and definitive proxy or information statements filed
pursuant to Section 13(a), 13(c), 14 or 15(d) of the 1934 Act after the date of
this Registration Statement and prior to the filing of a post-effective
amendment which indicates that all securities offered hereby have been sold or
which de-registers all securities then remaining unsold shall be deemed to be
incorporated by reference into this Registration Statement and to be a part
hereof from the date of filing of such documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference herein shall be
deemed to be modified or superseded for purposes of this Registration Statement
to the extent that a statement contained herein or in any subsequently filed
document which also is deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

Item 4. Description of Securities

        Not Applicable.

Item 5. Interests of Named Experts and Counsel

        Not Applicable.

Item 6. Indemnification of Directors and Officers

        The Registrant's Certificate of Incorporation limits the liability of
directors to the maximum extent permitted by Delaware law. Delaware law provides
that directors of a corporation will not be personally liable for monetary
damages for breach of their fiduciary duties as directors, except for liability
for (i) any breach of their duty of loyalty to the corporation or its
stockholders, (ii) acts or omissions not in good faith or that involve
intentional misconduct or a knowing violation of law, (iii) unlawful payments of
dividends or unlawful stock repurchases or redemptions as provided in Section
174 of the Delaware General Corporation Law, or (iv) any transaction from which
the director derives an improper personal benefit.

        The Registrant's Bylaws provide that the Registrant shall indemnify its
directors and may indemnify its officers, employees and other agents to the
fullest extent permitted by law. The Registrant believes that indemnification
under its Bylaws covers at least negligence and gross negligence on the part of
an indemnified party in connection with the defense of any action or proceeding
arising out of such party's status or service as a director, officer, employee
or other agent of the Company upon an undertaking by such party to repay such
advances if it is ultimately determined that such party is not entitled to
indemnification. The Registrant has entered into

                                      II-1
3

Indemnification Agreements with its officers and directors. The Indemnification
Agreements provide the Registrant's officers and directors with further
indemnification to the maximum extent permitted by the Delaware General
Corporation Law.

Item 7. Exemption from Registration Claimed

        Not Applicable.

Item 8. Exhibits
Exhibit Number      Exhibit
--------------      -------
4.0            Instruments Defining Rights of Stockholders. Reference is
                    made to the Registrant's Registration Statement No.
                    000-24009 on Form 8-A and the exhibits thereto, which are
                    incorporated herein by reference pursuant to Item 3(d) of
                    this Registration Statement.

     5.0            Opinion of Brobeck, Phleger & Harrison LLP.

    23.1            Consent of Independent Auditors

    23.2            Consent of Brobeck, Phleger & Harrison LLP is contained in
                    Exhibit 5.

    24.0            Power of Attorney. Reference is made to page II-3 of this
                    Registration Statement.

    99.1            Com21, Inc. 1998 Stock Incentive Plan (Amended and Restated
                    As of March 1999).

    99.2            Com21, Inc. 1998 Employee Stock Purchase Plan (Amended and
                    Restated as of January 12, 2000).

    99.3            Com21, Inc. 2000 Stock Option Plan.
Item 9. Undertakings

        A. The undersigned Registrant hereby undertakes: (1) to file, during any
period in which offers or sales are being made, a post-effective amendment to
this Registration Statement (i) to include any prospectus required by Section
10(a)(3) of the 1933 Act, (ii) to reflect in the prospectus any facts or events
arising after the effective date of this Registration Statement (or the most
recent post-effective amendment thereof) which, individually or in the
aggregate, represent a fundamental change in the information set forth in this
Registration Statement and (iii) to include any material information with
respect to the plan of distribution not previously disclosed in this
Registration Statement or any material change to such information in this
Registration Statement; provided, however, that clauses (1)(i) and (1)(ii) shall
not apply if the information required to be included in a post-effective
amendment by those clauses is contained in periodic reports filed by the
Registrant pursuant to Section 13 or Section 15(d) of the 1934 Act that are
incorporated by reference into this Registration Statement; (2) that for the
purpose of determining any liability under the 1933 Act each such post-effective
amendment shall be deemed to be a new registration statement relating to the
securities offered therein and the offering of such securities at that time
shall be deemed to be the initial bona fide offering thereof; and (3) to remove
from registration by means of a post-effective amendment any of the securities
being registered which remain unsold at the termination of the Registrant's 1998
Stock Incentive Plan, 1998 Employee Stock Purchase Plan and/or 2000 Stock Option
Plan.

        B. The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the 1933 Act, each filing of the Registrant's
annual report pursuant to Section 13(a) or Section 15(d) of the 1934 Act that is
incorporated by reference into this Registration Statement shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

        C. Insofar as indemnification for liabilities arising under the 1933 Act
may be permitted to directors, officers or controlling persons of the Registrant
pursuant to the indemnification provisions summarized in Item 6 or otherwise,
the Registrant has been advised that, in the opinion of the Commission, such
indemnification is against public policy as expressed in the 1933 Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the Registrant of expenses incurred
or paid by a director, officer, or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the 1933 Act and will be governed by the final
adjudication of such issue.

                                      II-2
4

                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8, and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Milpitas, State of California on 9th day of
June, 2000.

                                            COM21, INC.

                                            By: /s/ Peter D. Fenner
                                               ---------------------------------
                                               Peter D. Fenner
                                               President, Chief Executive
                                               Officer and Director

                                POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS:

        That the undersigned officers and directors of Com21, Inc., a Delaware
corporation, do hereby constitute and appoint Peter D. Fenner and David L.
Robertson and each of them, the lawful attorneys-in-fact and agents with full
power and authority to do any and all acts and things and to execute any and all
instruments which said attorneys and agents, and any one of them, determine may
be necessary or advisable or required to enable said corporation to comply with
the Securities Act of 1933, as amended, and any rules or regulations or
requirements of the Securities and Exchange Commission in connection with this
Registration Statement. Without limiting the generality of the foregoing power
and authority, the powers granted include the power and authority to sign the
names of the undersigned officers and directors in the capacities indicated
below to this Registration Statement, to any and all amendments, both
pre-effective and post-effective, and supplements to this Registration
Statement, and to any and all instruments or documents filed as part of or in
conjunction with this Registration Statement or amendments or supplements
thereof, and each of the undersigned hereby ratifies and confirms that all said
attorneys and agents, or any one of them, shall do or cause to be done by virtue
hereof. This Power of Attorney may be signed in several counterparts.

        IN WITNESS WHEREOF, each of the undersigned has executed this Power of
Attorney as of the date indicated.

        Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.
Signature                      Title                                            Date
---------                      -----                                            ----
/s/ Peter D. Fenner            President, Chief Executive Officer and           June 9, 2000
------------------------       Director (Principal Executive Officer)
Peter D. Fenner

/s/ David L. Robertson         Chief Financial Officer, Vice President,         June 22, 2000
------------------------       Finance and Administration, Corporate
David L. Robertson             Secretary (Principal Financial Officer)

/s/ Paul Baran                 Chairman of the Board of Directors               June 22, 2000
------------------------
Paul Baran
II-3
5
/s/ C. Richard Kramlich        Director                                         June 22, 2000
-----------------------
C. Richard Kramlich

/s/ Robert C. Hawk             Director                                         June 22, 2000
-----------------------
Robert C. Hawk

                               Director
-----------------------
Jerald L. Kent

/s/ Daniel J. Pike             Director                                         June 22, 2000
-----------------------
Daniel J. Pike

/s/ Robert W. Wilmot           Director                                         June 22, 2000
-----------------------
Robert W. Wilmot

                               Director
-----------------------
James J. Spilker, Jr.
II-4
6

EXHIBIT INDEX
Exhibit Number      Exhibit
--------------      -------
4.0            Instruments Defining Rights of Stockholders. Reference is
                    made to the Registrant's Registration Statement No.
                    000-24009 on Form 8-A and the exhibits thereto, which are
                    incorporated herein by reference pursuant to Item 3(d) of
                    this Registration Statement.

     5.0            Opinion of Brobeck, Phleger & Harrison LLP.

    23.1            Consent of Independent Auditors

    23.2            Consent of Brobeck, Phleger & Harrison LLP is contained in
                    Exhibit 5.

    24.0            Power of Attorney. Reference is made to page II-3 of this
                    Registration Statement.

    99.1            Com21, Inc. 1998 Stock Incentive Plan (Amended and Restated
                    as of March 1999).

    99.2            Com21, Inc. 1998 Employee Stock Purchase Plan (Amended and
                    Restated as of January 12, 2000).

    99.3            Com21, Inc. 2000 Stock Option Plan.