<PAGE>   1

================================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                             -----------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                        UNDER THE SECURITIES ACT OF 1933

                            ------------------------

                                   N2H2, INC.
             (Exact name of registrant as specified in its charter)

           Washington                                 91-1686754
  (State or other jurisdiction           (I.R.S. Employer Identification No.)
of incorporation or organization)
                                                    John F. Duncan
  900 Fourth Avenue, Suite 3400              900 Fourth Avenue, Suite 3400
    Seattle, Washington 98164                  Seattle, Washington 98164
 (Address of Principal Executive                    (206) 336-1501
  Offices, including zip code)           (Name, address and telephone number,
                                      including area code, of agent for service)

                        N2H2, Inc. 2000 Stock Option Plan
                          Employee Stock Purchase Plan
                              (Full Title of Plans)

                                   Copies to:
                               Gregory L. Anderson
                                 William W. Lin
                         Lane Powell Spears Lubersky LLP
                          1420 Fifth Avenue, Suite 4100
                         Seattle, Washington 98101-2338

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
=============================================================================================================
                                                        Proposed Maximum  Proposed Maximum
   Title of Securities                   Amount To Be    Offering Price      Aggregate         Amount of
    To Be Registered                     Registered(1)    Per Share(2)    Offering Price(2)  Registration Fee
-------------------------------------------------------------------------------------------------------------
<S>                                      <C>            <C>               <C>                <C>
N2H2, Inc. 2000 Stock Option Plan
  Common stock, no par value              4,000,000         $12.8125       $51,250,000        $13,530.00

Employee Stock Purchase Plan
  Common stock, no par value                750,000         $12.8125       $ 9,609,375        $ 2,536.88

          Total                           4,750,000                        $60,859,375        $16,066.88
==========================================================================================================
</TABLE>

(1) Together with an indeterminate number of additional shares of common stock
which may be necessary to adjust the number of shares of common stock reserved
for issuance pursuant to the Plans as the result of any future stock split,
stock dividend or similar adjustment of the outstanding common stock of N2H2.

(2) Estimated solely for the purpose of calculating the registration fee
pursuant to Rule 457(c) and 457(h) under the Securities Act of 1933 for shares
of common stock reserved under the N2H2, Inc. 2000 Stock Option Plan and
Employee Stock Purchase Plan. The price per share is estimated to be $12.8125
based on the average of the high ($14.5625) and low ($11.0625) sales prices for
the Common Stock on March 30, 2000 as reported on the Nasdaq National Market.

================================================================================


<PAGE>   2


                                     PART II

                             INFORMATION REQUIRED IN
                           THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.

The following documents filed with the Securities and Exchange Commission (the
"Commission") are hereby incorporated by reference in this registration
statement:

        (a)    N2H2's latest Annual Report on Form 10-K for the fiscal year
               ended September 30, 1999 filed with the Commission on December
               30, 1999.

        (b)    All other reports filed by N2H2 pursuant to Section 13(a) or
               15(d) of the Securities and Exchange Act of 1934, as amended (the
               "Exchange Act"), since the end of the fiscal year covered by the
               Annual Report on Form 10-K referred to in (a) above, including
               N2H2's Quarterly Report on Form 10-Q for the quarter ended
               December 31, 1999 filed with the Commission on February 14, 2000,
               and N2H2's Current Report on Form 8-K filed with the Commission
               on March 24, 2000; and

        (c)    The description of N2H2's common stock contained in Amendment No.
               3 to the Registrant's Registration Statement on Form S-1
               (Registration No. 333-78495) filed with the Commission on July
               20, 1999, including any amendment or report filed for the purpose
               of updating such description.

All documents subsequently filed by N2H2 pursuant to Sections 13(a), 13(c), 14
and 15(d) of the Exchange Act, prior to the filing of a post-effective amendment
which indicates that the securities offered hereby have been sold or which
deregisters 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 such documents.

ITEM 4. DESCRIPTION OF SECURITIES.

Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

The legality of the common stock being registered is being passed upon by Lane
Powell Spears Lubersky LLP. On March 30, 2000, members of that firm owned
directly or indirectly an aggregate of approximately 60,320 shares of common
stock of N2H2, Inc.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

N2H2's restated articles of incorporation include a provision that limits the
liability of directors to the fullest extent permitted by the Washington
Business Corporation Act as it currently exists or as it may be amended in the
future. Consequently, subject to the Washington Business Corporation Act, no
director will be personally liable to N2H2 or its shareholders for monetary
damages resulting from his or her conduct as a director of N2H2, except
liability for:

        -      acts or omissions involving intentional misconduct or knowing
               violations of law,

        -      unlawful distributions, or

        -      transactions from which the director personally receives a
               benefit in money, property or services to which the director is
               not legally entitled.


<PAGE>   3

The restated articles of incorporation also provide that N2H2 will indemnify any
individual made a party to a proceeding because that individual is or was a
director of N2H2. N2H2 will also advance or reimburse reasonable expenses
incurred by that individual prior to the final disposition of the proceeding to
the fullest extent permitted by applicable law. In addition, N2H2 maintains
director and officer liability insurance coverage under which its directors and
officers may be indemnified against any liability they may incur for serving as
directors and officers of N2H2.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

Not applicable.

ITEM 8. EXHIBITS.

<TABLE>
<CAPTION>
Exhibit
Number         Description
-------        -----------
<S>            <C>
 5.1           Opinion of Lane Powell Spears Lubersky LLP (filed herewith)

10.1           N2H2, Inc. 2000 Stock Option Plan (filed herewith)

10.2           Employee Stock Purchase Plan (filed herewith)

23.1           Consent of Independent Accountants (filed herewith)

23.2           Consent of Lane Powell Spears Lubersky LLP (included in Exhibit
               5.1)

24.1           Power of Attorney (see signature page)
</TABLE>

ITEM 9. UNDERTAKINGS.

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
Securities 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 paragraphs (1)(i) and (1)(ii) above do not apply if the
registration statement is on Form S-3, Form S-8 or Form F-3, and the information
required to be included in a post-effective amendment by those paragraphs is
contained in periodic reports filed with or furnished to the Commission by the
Registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are
incorporated by reference in this registration statement.

        (2) That, for the purpose of determining any liability under the
Securities 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.

        (3) To remove from registration by means of a post-effective amendment


<PAGE>   4

any of the securities being registered which remain unsold at the termination of
the offering.

That, for purposes of determining any liability under the Securities Act, each
filing of the Registrant's annual report pursuant to Section 13(a) or 15(d) of
the Exchange Act (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in 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.

Insofar as indemnification for liabilities arising under the Securities Act may
be permitted to directors, officers and controlling persons of the Registrant
pursuant to the foregoing provisions, or otherwise, the Registrant has been
advised that in the opinion of the Commission such indemnification is against
public policy as expressed in the Securities 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 Securities Act and will be governed by the final
adjudication of such issue.


                            [Signature Pages Follow]


<PAGE>   5


                                   SIGNATURES

Pursuant to the requirements of the Securities Act, 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 Seattle, State of Washington, on the 3rd day of April, 2000.

                                   N2H2, INC.

                                   /s/ John F. Duncan
                                   ---------------------------------------
                                   By:  John F. Duncan, Vice President --
                                        Chief Financial Officer, Secretary
                                        and Treasurer


<PAGE>   6


                                POWER OF ATTORNEY

Each person whose individual signature appears below hereby authorizes Peter H.
Nickerson and John F. Duncan, or either of them, as attorney-in-fact with full
power of substitution, to execute in the name and on the behalf of each person,
individually and in each capacity stated below, and to file, any and all
amendments to this registration statement, including any and all post-effective
amendments, and any related Rule 462(b) registration statement and any amendment
thereto.

Pursuant to the requirements of the Securities Act, this registration statement
has been signed by the following persons in the capacities indicated below on
the 3rd day of April, 2000.


<TABLE>
<CAPTION>
SIGNATURE                           TITLE
---------                           -----
<S>                                 <C>

/s/ PETER H. NICKERSON              Chief Executive Officer, President and
------------------------------      Chairman of the Board (Principal Executive
    Peter H. Nickerson              Officer)

/s/ JOHN F. DUNCAN                  Vice President -- Chief Financial Officer,
------------------------------      Secretary and Treasurer(Principal Accounting
    John F. Duncan                  and Financial Officer)

/s/ HOLLIS R. HILL                  Director
------------------------------
    Hollis R. Hill

/s/ MARK A. SEGALE                  Director
------------------------------
    Mark A. Segale

/s/ RICHARD R. ROWE                 Director
------------------------------
    Richard R. Rowe
</TABLE>


<PAGE>   7



                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit
Number                               Description
-------                              -----------
<S>            <C>

 5.1           Opinion of Lane Powell Spears Lubersky LLP (filed herewith)

10.1           N2H2, Inc. 2000 Stock Option Plan (filed herewith)

10.2           Employee Stock Purchase Plan (filed herewith)

23.1           Consent of Independent Accountants (filed herewith)

23.2           Consent of Lane Powell Spears Lubersky LLP (included in Exhibit
               5.1)

24.1           Power of Attorney (see signature page)
</TABLE>
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 14794}]
{"company-data": {"conformed-name": "N2H2 INC", "cik": "0001077301", "assigned-sic": "4899", "irs-number": "911686754", "state-of-incorporation": "WA", "fiscal-year-end": "0930"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-33954", "film-number": "593105"}, "business-address": {"street1": "900 FOURTH AVE", "street2": "SUITE 3400", "city": "SEATTLE", "state": "WA", "zip": "98164", "phone": "2063361555"}, "mail-address": {"street1": "N2H2, INC.", "street2": "900 4TH AVENUE, SUITE 3400", "city": "SEATTLE", "state": "WA", "zip": "98164"}}
1

================================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                             -----------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                        UNDER THE SECURITIES ACT OF 1933

                            ------------------------

                                   N2H2, INC.
             (Exact name of registrant as specified in its charter)

           Washington                                 91-1686754
  (State or other jurisdiction           (I.R.S. Employer Identification No.)
of incorporation or organization)
                                                    John F. Duncan
  900 Fourth Avenue, Suite 3400              900 Fourth Avenue, Suite 3400
    Seattle, Washington 98164                  Seattle, Washington 98164
 (Address of Principal Executive                    (206) 336-1501
  Offices, including zip code)           (Name, address and telephone number,
                                      including area code, of agent for service)

                        N2H2, Inc. 2000 Stock Option Plan
                          Employee Stock Purchase Plan
                              (Full Title of Plans)

                                   Copies to:
                               Gregory L. Anderson
                                 William W. Lin
                         Lane Powell Spears Lubersky LLP
                          1420 Fifth Avenue, Suite 4100
                         Seattle, Washington 98101-2338

                         CALCULATION OF REGISTRATION FEE
=============================================================================================================
                                                        Proposed Maximum  Proposed Maximum
   Title of Securities                   Amount To Be    Offering Price      Aggregate         Amount of
    To Be Registered                     Registered(1)    Per Share(2)    Offering Price(2)  Registration Fee
-------------------------------------------------------------------------------------------------------------
N2H2, Inc. 2000 Stock Option Plan
  Common stock, no par value              4,000,000         $12.8125       $51,250,000        $13,530.00

Employee Stock Purchase Plan
  Common stock, no par value                750,000         $12.8125       $ 9,609,375        $ 2,536.88

          Total                           4,750,000                        $60,859,375        $16,066.88
==========================================================================================================
(1) Together with an indeterminate number of additional shares of common stock
which may be necessary to adjust the number of shares of common stock reserved
for issuance pursuant to the Plans as the result of any future stock split,
stock dividend or similar adjustment of the outstanding common stock of N2H2.

(2) Estimated solely for the purpose of calculating the registration fee
pursuant to Rule 457(c) and 457(h) under the Securities Act of 1933 for shares
of common stock reserved under the N2H2, Inc. 2000 Stock Option Plan and
Employee Stock Purchase Plan. The price per share is estimated to be $12.8125
based on the average of the high ($14.5625) and low ($11.0625) sales prices for
the Common Stock on March 30, 2000 as reported on the Nasdaq National Market.

================================================================================
2

                                     PART II

                             INFORMATION REQUIRED IN
                           THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE.

The following documents filed with the Securities and Exchange Commission (the
"Commission") are hereby incorporated by reference in this registration
statement:

        (a)    N2H2's latest Annual Report on Form 10-K for the fiscal year
               ended September 30, 1999 filed with the Commission on December
               30, 1999.

        (b)    All other reports filed by N2H2 pursuant to Section 13(a) or
               15(d) of the Securities and Exchange Act of 1934, as amended (the
               "Exchange Act"), since the end of the fiscal year covered by the
               Annual Report on Form 10-K referred to in (a) above, including
               N2H2's Quarterly Report on Form 10-Q for the quarter ended
               December 31, 1999 filed with the Commission on February 14, 2000,
               and N2H2's Current Report on Form 8-K filed with the Commission
               on March 24, 2000; and

        (c)    The description of N2H2's common stock contained in Amendment No.
               3 to the Registrant's Registration Statement on Form S-1
               (Registration No. 333-78495) filed with the Commission on July
               20, 1999, including any amendment or report filed for the purpose
               of updating such description.

All documents subsequently filed by N2H2 pursuant to Sections 13(a), 13(c), 14
and 15(d) of the Exchange Act, prior to the filing of a post-effective amendment
which indicates that the securities offered hereby have been sold or which
deregisters 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 such documents.

ITEM 4. DESCRIPTION OF SECURITIES.

Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

The legality of the common stock being registered is being passed upon by Lane
Powell Spears Lubersky LLP. On March 30, 2000, members of that firm owned
directly or indirectly an aggregate of approximately 60,320 shares of common
stock of N2H2, Inc.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

N2H2's restated articles of incorporation include a provision that limits the
liability of directors to the fullest extent permitted by the Washington
Business Corporation Act as it currently exists or as it may be amended in the
future. Consequently, subject to the Washington Business Corporation Act, no
director will be personally liable to N2H2 or its shareholders for monetary
damages resulting from his or her conduct as a director of N2H2, except
liability for:

        -      acts or omissions involving intentional misconduct or knowing
               violations of law,

        -      unlawful distributions, or

        -      transactions from which the director personally receives a
               benefit in money, property or services to which the director is
               not legally entitled.
3

The restated articles of incorporation also provide that N2H2 will indemnify any
individual made a party to a proceeding because that individual is or was a
director of N2H2. N2H2 will also advance or reimburse reasonable expenses
incurred by that individual prior to the final disposition of the proceeding to
the fullest extent permitted by applicable law. In addition, N2H2 maintains
director and officer liability insurance coverage under which its directors and
officers may be indemnified against any liability they may incur for serving as
directors and officers of N2H2.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

Not applicable.

ITEM 8. EXHIBITS.
Exhibit
Number         Description
-------        -----------
5.1           Opinion of Lane Powell Spears Lubersky LLP (filed herewith)

10.1           N2H2, Inc. 2000 Stock Option Plan (filed herewith)

10.2           Employee Stock Purchase Plan (filed herewith)

23.1           Consent of Independent Accountants (filed herewith)

23.2           Consent of Lane Powell Spears Lubersky LLP (included in Exhibit
               5.1)

24.1           Power of Attorney (see signature page)
ITEM 9. UNDERTAKINGS.

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
Securities 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 paragraphs (1)(i) and (1)(ii) above do not apply if the
registration statement is on Form S-3, Form S-8 or Form F-3, and the information
required to be included in a post-effective amendment by those paragraphs is
contained in periodic reports filed with or furnished to the Commission by the
Registrant pursuant to Section 13 or Section 15(d) of the Exchange Act that are
incorporated by reference in this registration statement.

        (2) That, for the purpose of determining any liability under the
Securities 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.

        (3) To remove from registration by means of a post-effective amendment
4

any of the securities being registered which remain unsold at the termination of
the offering.

That, for purposes of determining any liability under the Securities Act, each
filing of the Registrant's annual report pursuant to Section 13(a) or 15(d) of
the Exchange Act (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in 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.

Insofar as indemnification for liabilities arising under the Securities Act may
be permitted to directors, officers and controlling persons of the Registrant
pursuant to the foregoing provisions, or otherwise, the Registrant has been
advised that in the opinion of the Commission such indemnification is against
public policy as expressed in the Securities 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 Securities Act and will be governed by the final
adjudication of such issue.

                            [Signature Pages Follow]
5

                                   SIGNATURES

Pursuant to the requirements of the Securities Act, 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 Seattle, State of Washington, on the 3rd day of April, 2000.

                                   N2H2, INC.

                                   /s/ John F. Duncan
                                   ---------------------------------------
                                   By:  John F. Duncan, Vice President --
                                        Chief Financial Officer, Secretary
                                        and Treasurer
6

                                POWER OF ATTORNEY

Each person whose individual signature appears below hereby authorizes Peter H.
Nickerson and John F. Duncan, or either of them, as attorney-in-fact with full
power of substitution, to execute in the name and on the behalf of each person,
individually and in each capacity stated below, and to file, any and all
amendments to this registration statement, including any and all post-effective
amendments, and any related Rule 462(b) registration statement and any amendment
thereto.

Pursuant to the requirements of the Securities Act, this registration statement
has been signed by the following persons in the capacities indicated below on
the 3rd day of April, 2000.
SIGNATURE                           TITLE
---------                           -----
/s/ PETER H. NICKERSON              Chief Executive Officer, President and
------------------------------      Chairman of the Board (Principal Executive
    Peter H. Nickerson              Officer)

/s/ JOHN F. DUNCAN                  Vice President -- Chief Financial Officer,
------------------------------      Secretary and Treasurer(Principal Accounting
    John F. Duncan                  and Financial Officer)

/s/ HOLLIS R. HILL                  Director
------------------------------
    Hollis R. Hill

/s/ MARK A. SEGALE                  Director
------------------------------
    Mark A. Segale

/s/ RICHARD R. ROWE                 Director
------------------------------
    Richard R. Rowe
7

                                INDEX TO EXHIBITS
Exhibit
Number                               Description
-------                              -----------
5.1           Opinion of Lane Powell Spears Lubersky LLP (filed herewith)

10.1           N2H2, Inc. 2000 Stock Option Plan (filed herewith)

10.2           Employee Stock Purchase Plan (filed herewith)

23.1           Consent of Independent Accountants (filed herewith)

23.2           Consent of Lane Powell Spears Lubersky LLP (included in Exhibit
               5.1)

24.1           Power of Attorney (see signature page)