SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 AMENDMENT NO. 1
                                       to
                                    FORM 20-F

(Mark One)

|_| REGISTRATION STATEMENT PURSUANT TO SECTION 12(b) OR (g) OF THE SECURITIES
EXCHANGE ACT OF 1934

OR

|X| ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT
OF 1934

For the fiscal year ended April 25, 2004

OR

|_| TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
ACT OF 1934

For the transition period from _________________ to ________________

                         Commission file number: 0-49984

                           MITEL NETWORKS CORPORATION
             (Exact name of Registrant as specified in its charter)

                                     Canada
                 (Jurisdiction of incorporation or organization)

                                350 Legget Drive
                         Ottawa, Ontario, Canada K2K 2W7
                    (Address of principal executive offices)

Securities registered or to be registered pursuant to Section 12(b) of the Act:
None

Securities registered or to be registered pursuant to Section 12(g) of the Act:

                        Common Shares, Without Par Value
                                (Title of Class)

Securities for which there is a reporting obligation pursuant to Section 15(d)
of the Act: None

Indicate the number of outstanding shares of each of the issuer's classes of
capital or common stock as of the close of the period covered by the annual
report: 111,688,279 common shares, 20,000,000 Class A Convertible Preferred
Shares and 67,249,944 Class B Convertible Preferred Shares as of July 27, 2004.

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. Yes |X| No |_|

Indicate by check mark which financial statement item the registrant has elected
to follow. Item 17 |_| Item 18 |X|


<PAGE>

Item 19. Exhibits

1     Articles of Incorporation and bylaws as currently in effect:

            1.1   Articles of Incorporation and amendments thereto prior to
                  April 22, 2004X

            1.2   Articles of Amendment dated April 22, 2004 X

            1.3   Articles of Amendment dated April 23, 2004 X

            1.4   Bylaws X


2     Instruments defining the rights of holders of equity securities being
      registered:

            2.1   See Articles of Incorporation described above in Exhibit 1.1,
                  Articles of Amendment dated April 22, 2004 described above in
                  Exhibit 1.2, and Articles of Amendment dated April 23, 2004
                  described above in Exhibit 1.3

            2.2   Specimen Common Share certificate*

            2.3   Specimen Series A Share certificate X

            2.4   Specimen Series B Share certificate X

4     Material contracts:

            4.1   Shareholders Agreement between Mitel Networks, Mitel
                  Knowledge, PTIC, Zarlink, Mitel Systems (now Wesley Clover),
                  WCC (now Wesley Clover), EdgeStone, and Dr. Matthews, dated
                  April 23, 2004**

            4.2   Class A Convertible Preferred Share Subscription Agreement
                  between Mitel Networks and EdgeStone dated April 23, 2004

            4.3   Registration Rights Agreement between Mitel Networks, Mitel
                  Knowledge, PTIC, Zarlink, EdgeStone, Mitel Systems (now Wesley
                  Clover) and WCC (now Wesley Clover), dated April 23, 2004**

            4.4   Receivables Purchase Agreement between the Mitel Group and The
                  Canada Trust Company effective date of April 16, 2004 X++

            4.5   Amended and Restated Credit Agreement between Mitel Networks,
                  the Lenders from time to time and Bank of Montreal as
                  Administrative Agent dated April 21, 2004 X++, as amended July
                  24, 2004 X

            4.6   Loan Agreement between MNL and Export Development Canada dated
                  March 4, 2003, as amended***

            4.7   Chattel Mortgage Loan Agreement between MNL and Barclays Bank
                  PLC dated October 22, 2001*

            4.8   Chattel Mortgage Loan Agreement between MNL and Barclays Bank
                  PLC dated April 25, 2003***


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<PAGE>

            4.9   Real Property Loan Facility between MNL and Barclays Bank PLC
                  dated December 13, 2001, secured by a legal charge dated
                  January 24, 2002*

            4.10  Business Overdraft and Ancillary Facility Agreement between
                  MNL and Barclays Bank PLC dated August 30, 2002***

            4.11  Supply Agreement between Mitel Networks and its subsidiaries
                  and BreconRidge and its subsidiaries dated August 30, 2001,
                  and related amendment dated February 27, 2003*+

            4.12  Amendment to the Supply Agreement between Mitel Networks and
                  its subsidiaries and BreconRidge and its subsidiaries dated
                  February 27, 2003***

            4.13  Sublease Agreement between Mitel Networks Corporation and
                  BreconRidge dated August 31, 2001 and First Amendment of
                  Sublease Agreement between Mitel Networks and BreconRidge
                  dated May 31, 2002*+

            4.14  Lease Agreement between MNL and BreconRidge dated September
                  14, 2001*

            4.15  Asset Sale Agreement between Mitel Networks and BreconRidge
                  MSCdated August 31, 2001*+

            4.16  Supply Agreement between Mitel Networks and Zarlink (formerly
                  Mitel Corporation) dated February 16, 2001 and related
                  amendment dated October 24, 2001*+, amended by Amending
                  Agreement dated April 23, 2004 X

            4.17  Lease Agreement between MNL and Zarlink Semiconductor Limited
                  (formerly Mitel Semiconductor Limited), a subsidiary of
                  Zarlink dated February 2, 2001*

            4.18  Intellectual Property License Agreement between Mitel Networks
                  and Zarlink (formerly Mitel Corporation) dated February 16,
                  2001*+

            4.19  Amendment to the Intellectual Property License Agreement
                  between Mitel Networks and Zarlink dated October 24, 2001*

            4.20  Non Competition and Non Solicitation Agreement between Zarlink
                  (formerly Mitel Corporation), Mitel Semiconductor V.N. Inc.,
                  Mitel Semiconductor Limited, Mitel Semiconductor Inc., 3755461
                  Canada Inc. (now Wesley Clover), Mitel Networks and MRPC dated
                  February 16, 2001*

            4.21  Lease Agreement between Mitel Networks and MRPC dated March
                  27, 2001*

            4.22  Strategic Alliance Agreement between Mitel Networks and March
                  Networks dated September 21, 2001*, as amended September 20,
                  2003 X

            4.23  Amended and Restated Employment Contract between Mitel
                  Networks and Donald Smith dated April 17, 2001* +

            4.24  Amended and Restated Employment Contract between Mitel
                  Networks and Paul Butcher dated February 16, 2001*+

            4.25  Union Agreement between MNSI (formerly Mitel Communications
                  Solutions, Inc.) and IBEW expiring on September 30, 2004*+


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<PAGE>

            4.26  Integrated Communications Solutions R&D Project Agreement
                  between Mitel Networks, Mitel Knowledge, March Networks and
                  Her Majesty the Queen in Right of Canada dated October 10,
                  2002 *+, as amended on March 27, 2003 and May 2, 2004
                  respectively X

            8.1   Subsidiaries of Mitel Networks Corporation*

            12.1  Certification by CEO pursuant to Section 302 of the
                  Sarbanes-Oxley Act of 2002

            12.2  Certification by CFO pursuant to Section 302 of the
                  Sarbanes-Oxley Act of 2002

            13.1  Certification by CEO pursuant to Section 906 of the
                  Sarbanes-Oxley Act of 2002

            13.2  Certification by CFO pursuant to Section 906 of the
                  Sarbanes-Oxley Act of 2002

----------
*     Filed as an exhibit to the Registration Statement on Form 20-F, as amended
      (File No. 0-49984) of Mitel Networks and incorporated herein by reference.

**    Filed on May 3, 2004 as an exhibit to a Schedule 13D (Mitel Networks as
      issuer) by EdgeStone Capital Equity Fund II-A, L.P.; EdgeStone Capital
      Equity Fund II-US, L.P.; EdgeStone Capital Equity Fund II-US-Inst., L.P.;
      National Bank Financial & Co. Inc.; EdgeStone Capital Equity Fund II-A GP,
      L.P.; EdgeStone Capital Equity Fund II US GP, L.P.; EdgeStone Capital
      Equity Fund II-US-Inst. GP, L.P.; EdgeStone Capital Equity Fund II-A GP,
      Inc.; EdgeStone Capital Equity Fund II-US Main GP, Inc.; EdgeStone Capital
      Equity Fund II-US-Inst. GP, Inc.; Samuel L. Duboc; Gilbert S. Palter;
      Bryan W. Kerdman; Sandra Cowan; and EdgeStone Capital Equity Fund II-B GP,
      Inc. and incorporated herein by reference.

***   Filed as an exhibit to the annual report on Form 20-F of Mitel Networks
      for the year ended April 27, 2003 and incorporated herein by reference.

x     Previously filed as part of this Annual Report.

+     Portions of this document have been granted "Confidential Treatment" by
      the Secretary of the Securities and Exchange Commission.

++    Portions of this document are subject to a pending Confidential Treatment
      Request filed with the Secretary of the Securities and Exchange
      Commission.


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<PAGE>

                                    SIGNATURE
                                    ---------

The registrant hereby certifies that it meets all of the requirements for filing
on Form 20-F and that it has duly caused and authorized the undersigned to sign
this annual report on its behalf.

                                                MITEL NETWORKS CORPORATION

                                                /s/ DONALD W. SMITH
                                                -------------------------------
                                                Name:  Donald W. Smith
                                                Title:  Chief Executive Officer

Date: December 22, 2004


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