<PAGE>   1

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM 8-K
                                 CURRENT REPORT

                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934



                                 Date of Report
                                  May 25, 1999



                        VOICESTREAM WIRELESS CORPORATION
               --------------------------------------------------
               (Exact Name of Registrant as Specified in Charter)


                                   Washington
                 ----------------------------------------------
                 (State or Other Jurisdiction of Incorporation)



            000-25441                                91-1956183
     ------------------------             ---------------------------------
     (Commission File Number)             (IRS Employer Identification No.)



                             3650 131st Avenue SE
                               Bellevue, WA 98006
                    ----------------------------------------
                    (Address of Principal Executive Offices)
                                   (Zip Code)

       Registrant's telephone number, including area code: (425) 653-4600
                                                           --------------



--------------------------------------------------------------------------------
          (Former Name or Former Address, if Changed Since Last Report)


<PAGE>   2



ITEM 5. OTHER EVENTS

    Sale of Senior Debentures to Nortel Networks Inc.

        Nortel Networks Inc. ("Nortel") purchased $400 million of 12% Series A
Senior Debentures Due 2011 (the "Senior Debentures") from VoiceStream Wireless
Corporation ("VoiceStream") in May 1999 pursuant to an indenture between
VoiceStream and Harris Trust Company of California. The Senior Debentures are
limited in aggregate principal amount to $400 million and will mature on May 15,
2011. Interest on the Senior Debentures accrues at 12% per annum and is payable
semiannually in arrears on November 15 and May 15 of each year. On or prior to
May 15, 2004, VoiceStream has the option to pay interest in cash or by issuance
of additional senior notes in the aggregate principal amount equal to the amount
of such interest.

        On or after May 15, 2004, the Senior Debentures are subject to
redemption at the option of VoiceStream, in whole or in part, at the redemption
prices set forth below plus accrued and unpaid interest thereon to the
applicable redemption date, if redeemed during the twelve-month period beginning
on May 15 of the years indicated below:

<TABLE>
<CAPTION>
                      YEAR                         PERCENTAGE
                      ----                         ----------
<S>                                                <C>
                      2004                         106.000%
                      2005                         104.500%
                      2006                         103.000%
                      2007                         101.500%
                      2008 and thereafter          100.000%
</TABLE>

        In addition, at any time prior to May 15, 2002, VoiceStream may redeem
with the proceeds of a public equity offering or strategic equity investment up
to 35% of the aggregate principal amount of the Senior Debentures, plus accrued
and unpaid interest thereon, if any, to the date of redemption, provided that at
least $260 million in aggregate principal amount of the Senior Debentures
remains outstanding immediately after such redemption.

        The indenture relating to the Senior Debentures contains certain
restrictive covenants which impose limitations on the operations and activities
of VoiceStream and its subsidiaries, including, but not limited to, limitations
on incurrence of additional indebtedness, issuance of preferred stock and
distributions and transfers by subsidiaries, creation of liens, disposition of
assets, transactions with affiliates and certain investments and transactions.

        The indenture relating to the Senior Debentures provides that (a) if
within 120 days from the original issuance of the Senior Debentures VoiceStream
consummates any Debt Offering (as defined in the indenture), and (b) if
VoiceStream delivers to Nortel an opinion of a reputable investment banking firm
to the effect that, taken as a whole, the covenants and events of default
governing the debt securities offered are not less favorable than the covenants
and events of default governing the Senior Debentures, then the covenants and
events of default governing the


<PAGE>   3

Senior Debentures shall be replaced with the covenants and events of default
governing the debt securities offered.

        The Purchase Agreement by and between VoiceStream and Nortel, dated May
14, 1999, is attached hereto as Exhibit 4.3. The Debenture Exchange and
Registration Rights Agreement by and between VoiceStream and Nortel, dated May
14, 1999, is attached hereto as Exhibit 4.4. The Indenture by and between
VoiceStream and Harris Trust Company, dated May 14, 1999, is attached hereto as
Exhibit 4.5.

        Amendment No. 6 to PCS 1900 Project and Supply Agreement

    On May 14, 1999, VoiceStream entered into Amendment No. 6 to PCS 1900
Project and Supply Agreement with Nortel Networks Inc. (the "Amendment"), a copy
of which is attached hereto as Exhibit 10.46. The Amendment and the underlying
agreement relate to the purchase and license of PCS cell-site and switching
systems and equipment, which includes hardware, software and related products
and services. Under the agreement, as amended, VoiceStream has committed to
purchase and license hardware, software and related products and services from
Nortel Networks Inc.

    On April 9, 1999, VoiceStream Wireless Corporation (formerly known as
Western PCS Corporation, a Delaware corporation ("WPCS")), merged with and into
VoiceStream, a Washington corporation, in order to effect a reincorporation of
WPCS in Washington State and, accordingly, VoiceStream succeeded to all of
WPCS's rights and obligations under the agreement to which the Amendment
relates. WPCS was formerly an 80.1% subsidiary of Western Wireless Corporation
("Western"). On May 3, 1999, VoiceStream legally separated from Western's other
operations in a tax-free spin-off. Western has previously filed: (a) the
underlying agreement, the PCS 190 Project and Supply Agreement dated June 30,
1995, by and between Western PCS Corporation and Nortel's predecessor (the
"Agreement"), with the Securities and Exchange Commission ("Commission") as
Exhibit 10.2 to Western's registration statement on Form S-1 (Commission Filing
No. 333-2432); (b) Amendment Nos. 1 and 2 to the Agreement, dated July 25, 1996
and October 25, 1996, respectively, with the Commission as Exhibits 10.43 and
10.44, respectively, to Western's registration statement on Form S-4
(Commission File No. 333-14859); (c) Amendment No. 3 to the Agreement, dated
October 14, 1996, with the Commission as Exhibit 10.42 to Western's Form 10-K
for fiscal year 1996 (Commission File No. 000-28160); and (d) Amendment No. 4
to the Agreement, dated March 26, 1998, with the Commission as Exhibit 10.70 to
Western's Form 10-Q/A for quarter ended June 30, 1998 (Commission File No.
000-28160). VoiceStream filed Amendment No. 5 to the Agreement, dated September
17, 1998, with the Commission as Exhibit 10.30 to VoiceStream's registration
statement on Form 10 (Commission File No. 000-25441).


<PAGE>   4




ITEM 7.  FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS

        (c)    Exhibits.

<TABLE>
<S>                   <C>
               4.3    Purchase Agreement by and between VoiceStream Wireless
                      Corporation and Nortel Networks Inc., dated May 14, 1999,
                      relating to 12% Series A Senior Debentures due 2011

               4.4    Debenture Exchange and Registration Rights Agreement by
                      and between VoiceStream Wireless Corporation and Nortel
                      Networks Inc., dated May 14, 1999, relating to 12% Series
                      A Senior Debentures due 2011

               4.5    Indenture by and between VoiceStream Wireless Corporation
                      and Harris Trust Company, dated May 14, 1999, relating to
                      12% Series A Senior Debentures due 2011 and 12% Senior
                      Debentures due 2011

               10.46  Amendment No. 6 to PCS 1900 Project and Supply Agreement
                      by and between VoiceStream Wireless Corporation and Nortel
                      Networks Inc.
</TABLE>





<PAGE>   5



                                   SIGNATURES


    Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                        VOICESTREAM WIRELESS CORPORATION

                                        Dated:  May 25, 1999

                                        By  /s/ Alan R. Bender
                                        ---------------------------------------
                                        Alan R. Bender
                                        Executive Vice President,
                                        General Counsel and Secretary




<PAGE>   6



                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
Number      Description
------      -----------
<S>         <C>
 4.3        Purchase Agreement by and between VoiceStream Wireless Corporation
            and Nortel Networks Inc., dated May 14, 1999, relating to 12% Series
            A Senior Debentures due 2011

 4.4        Debenture Exchange and Registration Rights Agreement by and between
            VoiceStream Wireless Corporation and Nortel Networks Inc., dated May
            14, 1999, relating to 12% Series A Senior Debentures due 2011

 4.5        Indenture by and between VoiceStream Wireless Corporation and Harris
            Trust Company, dated May 14, 1999, relating to 12% Series A Senior
            Debentures due 2011 and 12% Senior Debentures due 2011

10.46       Amendment No. 6 to PCS 1900 Project and Supply Agreement by and
            between VoiceStream Wireless Corporation and Nortel Networks Inc.
</TABLE>