<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   FORM 10-Q/A

(Mark One)
[X]    Quarterly report pursuant to Section 13 or 15(d) of the Securities 
       Exchange Act of 1934 for the quarterly period ended December 28, 1997 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:0-15086

                             SUN MICROSYSTEMS, INC.
             (Exact Name of registrant as specified in its charter)

            DELAWARE                                    94-2805249
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)


                    901 SAN ANTONIO ROAD, PALO ALTO, CA 94303
             (Address of principal executive offices with zip code)

Registrant's telephone number, including area code:    (650) 960-1300

                                       N/A
              (Former name, former address and former fiscal year,
                         if changed since last report)

  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 [ ]

                     APPLICABLE ONLY TO ISSUERS INVOLVED IN
                          BANKRUPTCY PROCEEDINGS DURING
                            THE PRECEDING FIVE YEARS:

  Indicate by check mark whether the registrant has filed all documents and
reports required to be filed by Section 12, 13 or 15(d) of the Securities
Exchange Act of 1934 subsequent to the distribution of securities under a plan
confirmed by a court.

                              YES  [ ]   NO [ ]

                      APPLICABLE ONLY TO CORPORATE ISSUERS:

  Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the latest practical date.

            CLASS                              OUTSTANDING AT DECEMBER 28, 1997
Common stock - $0.00067 par value                        377,366,835



<PAGE>   2

                                   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 thereunto duly authorized.



                                       SUN MICROSYSTEMS, INC.



                                       BY
                                           /s/    Michael E. Lehman
                                           -------------------------------------
                                           Michael E. Lehman
                                           Vice President, Corporate Resources 
                                           and Chief Financial Officer



                                           /s/     George Reyes
                                           -------------------------------------
                                           George Reyes
                                           Vice President and Corporate 
                                           Controller, Chief Accounting Officer



Dated:   July 15, 1998



                                       19
<PAGE>   3

                                  EXHIBIT INDEX


               27        Amended Financial Data Schedule