<PAGE>   1
 
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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                                  FORM 10-K/A
(MARK ONE)
 
     [X]   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
           SECURITIES EXCHANGE ACT OF 1934
 
                  FOR THE FISCAL YEAR ENDED DECEMBER 31, 1998
 
                                       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: 1-12478 (IRVINE APARTMENT COMMUNITIES, INC.)
 
                                   0-22569 (IRVINE APARTMENT COMMUNITIES, L.P.)
                                   1-13721 (IAC CAPITAL TRUST)
 
                       IRVINE APARTMENT COMMUNITIES, INC.
                       IRVINE APARTMENT COMMUNITIES, L.P.
                               IAC CAPITAL TRUST
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
 
<TABLE>
<S>                                            <C>
                   MARYLAND                                      33-0698698
                   DELAWARE                                      33-0587829
                   DELAWARE                                      91-6452946
           (STATE OF INCORPORATION)               (I.R.S. EMPLOYER IDENTIFICATION NUMBER)
</TABLE>
 
      550 NEWPORT CENTER DRIVE, SUITE 300, NEWPORT BEACH, CALIFORNIA 92660
                    (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
 
       REGISTRANTS' TELEPHONE NUMBER, INCLUDING AREA CODE: (949) 720-5500
 
          SECURITIES REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT:
 
<TABLE>
<S>                                            <C>
             TITLE OF EACH CLASS:                NAME OF EACH EXCHANGE ON WHICH REGISTERED:
               ----------------                    --------------------------------------
    COMMON STOCK, PAR VALUE $.01 PER SHARE             NEW YORK STOCK EXCHANGE, INC.;
     (IRVINE APARTMENT COMMUNITIES, INC.)                  PACIFIC EXCHANGE, INC.
      NUMBER OF SHARES OF COMMON STOCK OUTSTANDING AS OF DECEMBER 31, 1998: 20,163,643

                 SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT:

                                    TITLE OF EACH CLASS:
                                    --------------------
                            UNITS OF GENERAL PARTNERSHIP INTEREST
                            (IRVINE APARTMENT COMMUNITIES, L.P.)
               NUMBER OF UNITS OUTSTANDING AS OF DECEMBER 31, 1998: 20,163,643

                 SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT:

             TITLE OF EACH CLASS:                NAME OF EACH EXCHANGE ON WHICH REGISTERED:
             --------------------                ------------------------------------------
        SERIES A PREFERRED SECURITIES                  NEW YORK STOCK EXCHANGE, INC.
             (IAC CAPITAL TRUST)

             NUMBER OF SECURITIES OUTSTANDING AS OF DECEMBER 31, 1998: 6,000,000
</TABLE>
 
     Indicate by check mark whether the registrant has (1) 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 time as required), and
(2) has been subject to such filing requirements for the past 90 days:
 
<TABLE>
         <S>                                 <C>    <C>
         Irvine Apartment Communities, Inc.  Yes [X] No [ ]
         Irvine Apartment Communities, L.P.  Yes [X] No [ ]
         IAC Capital Trust                   Yes [X] No [ ]
</TABLE>
 
     Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of registrants' knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. [ ]
 
     The aggregate market value of the voting stock held by nonaffiliates of the
registrant as of January 31, 1999 was $531,666,000 assuming that all officers
and directors of the Company are affiliates.
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<PAGE>   2

EXPLANATORY NOTE:  This Annual Report on Form 10-K/A is being filed solely for 
the purpose of filing signed copies of Exhibits 23.1, 23.2 and 23.3, which 
were inadvertently misfiled on April 30, 1999.
<PAGE>   3
 
                                   SIGNATURES
 
     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrants have duly caused this Amended Report to be
signed on its behalf by the undersigned, thereunto duly authorized.
 
                                          IRVINE APARTMENT COMMUNITIES, INC.
 
   
Date: May 3, 1999                         By:        /s/ SHAWN HOWIE
    
                                            ------------------------------------
                                            Shawn Howie
                                            Interim Chief Financial Officer and
                                              Secretary
 
                                          IRVINE APARTMENT COMMUNITIES, L.P.
 
                                          By: Irvine Apartment Communities,
                                              Inc.,
                                            its sole general partner
 
   
Date: May 3, 1999                         By:        /s/ SHAWN HOWIE
    
                                            ------------------------------------
                                            Shawn Howie
                                            Interim Chief Financial Officer and
                                              Secretary
 
                                          IAC CAPITAL TRUST
 
   
Date: May 3, 1999                         By:        /s/ SHAWN HOWIE
    
                                            ------------------------------------
                                            Shawn Howie
                                            Regular Trustee
<PAGE>   4
 
                               INDEX TO EXHIBITS
 
<TABLE>
<CAPTION>
EXHIBIT
NUMBER                             DESCRIPTION
-------                            -----------
<S>        <C>
2.1.1      Agreement and Plan of Merger dated as of March 20, 1996
           between the Company and Irvine Apartment Communities, Inc.,
           a Delaware corporation (incorporated by reference to Exhibit
           2.1 of the Company's Registration Statement on Form 8-B,
           filed with the Securities and Exchange Commission on April
           30, 1996 (the "Form 8-B")).
2.2        Purchase and Sale Agreement and Joint Escrow Instructions
           dated April 18, 1997 by and between Aoki Construction (CA)
           Co., Ltd. and the Operating Partnership (incorporated by
           reference to Exhibit 2.1 of the Current Report on Form 8-K
           of the Company and the Operating Partnership filed on August
           6, 1997).
2.3        Agreement and Plan of Merger dated as of February 1, 1999,
           between TIC Acquisition LLC and the Company (incorporated by
           reference to Exhibit 2.1 of the Current Report on Form 8-K
           of the Company filed on February 2, 1999).
2.4        Stock Purchase Agreement dated as of February 1, 1999 among
           the Operating Partnership, as buyer, and William H.
           Thompson, Bruce Dorfman and Robert Hughes, as sellers.*
3.1        Articles of Amendment and Restatement of the Company
           (incorporated by reference to Exhibit 3.1 of the Form 8-B).
3.2        Articles of Merger dated May 2, 1996 between the Company and
           Irvine Apartment Communities, Inc., a Delaware corporation
           (incorporated by reference to Exhibit 14 of Amendment No. 5
           to Schedule 13D filed on July 15, 1996 by The Irvine
           Company, TIC Investment Company A, TIC Investment Company C
           and Donald L. Bren).
3.3        Amended Bylaws of the Company (incorporated by reference to
           Exhibit 3.2 of the Form 8-B).
3.4        Specimen of Certificate Representing Shares of Common Stock
           (incorporated by reference to Exhibit 3.3 of the Form 8-B).
3.5        Second Amended and Restated Agreement of Limited Partnership
           of Irvine Apartment Communities, L.P. dated January 20, 1998
           (incorporated by reference to Exhibit 3.5 of the Annual
           Report on Form 10-K of the Company and the Operating
           Partnership for the year ended December 31, 1997 (the "1997
           Form 10-K")).
3.5.1      Amendment No. 1 dated as of October 30, 1998 to the Second
           Amended and Restated Agreement of Limited Partnership of the
           Operating Partnership dated as of January 20, 1998.*
3.6        Designation Instrument dated January 20, 1998, relating to
           the Series A Preferred L.P. Units of the Operating
           Partnership (incorporated by reference to Exhibit 3.6 of the
           1997 Form 10-K).
3.6.1      Designation Instrument dated November 12, 1998, relating to
           the Series B Preferred L.P. Units of the Operating
           Partnership.*
4.1        Indenture dated as of October 1, 1997 between the Operating
           Partnership and First Trust of California, National
           Association, as Trustee (the "Trustee") (incorporated by
           reference to Exhibit 4.1 of the Current Report on Form 8-K
           of the Company and the Operating Partnership filed on
           October 1, 1997 (the "October 1997 Form 8-K")).
4.2        Supplemental Indenture No. 1 dated as of October 1, 1997,
           relating to the Operating Partnership's 7% Notes due 2007,
           between the Operating Partnership and the Trustee
           (incorporated by reference to Exhibit 4.2 of the October
           1997 Form 8-K).
4.3        Form of Series A Trust Preferred Security (included in
           Exhibit 4.5).
4.4        Amended and Restated Declaration of Trust dated January 20,
           1998 of IAC Capital Trust (incorporated by reference to
           Exhibit 4.4 of the 1997 Form 10-K).
4.5        Certificate of Terms dated January 20, 1998 Relating to
           Series A Preferred Securities of IAC Capital Trust
           (incorporated by reference to Exhibit 4.5 of the 1997 Form
           10-K).
</TABLE>
<PAGE>   5
 
<TABLE>
<CAPTION>
EXHIBIT
NUMBER                             DESCRIPTION
-------                            -----------
<S>        <C>
4.6        Officer's Certificate dated April 9, 1998 setting forth
           certain terms and provisions applicable to the Operating
           Partnership's Medium-Term Notes, Series A (incorporated by
           reference to Exhibit 4.1 of the Current Report on Form 8-K
           of the Company and the Operating Partnership filed on April
           10, 1998 (the "MTN 8-K")).
4.7        Form of the Operating Partnership's Fixed Rate Medium-Term
           Note, Series A (incorporated by reference to Exhibit 4.2 of
           the MTN 8-K).
4.8        Form of the Operating Partnership's Floating Rate
           Medium-Term Note, Series A (incorporated by reference to
           Exhibit 4.3 of the MTN 8-K).
4.9        Supplemental Indenture No. 2 dated as of April 9, 1998 to
           the Indenture dated as of October 1, 1997 between the
           Operating Partnership and U.S. Bank Trust National
           Association, trustee (incorporated by reference to Exhibit
           4.4 of the MTN 8-K).
10.1       Purchase and Sale Agreement and Joint Escrow Instructions
           dated April 18, 1997 by and between Aoki Construction (CA)
           Co., Ltd. and the Operating Partnership (see Exhibit 2.2).
10.2       Lease Agreement (incorporated by reference to Exhibit 10.2
           of the Annual Report on Form 10-K of the Company for the
           year ended December 31, 1993 (the "1993 Form 10-K").
10.3       Employment Agreement with Former Senior Vice President,
           Chief Financial Officer and Secretary (incorporated by
           reference to Exhibit 10.3 of the 1997 Form 10-K).
10.3.1     Confidentiality Agreement and General Release dated as of
           October 13, 1998 between the Company and the former Senior
           Vice President, Chief Financial Officer and Secretary.*
10.4       Miscellaneous Rights Agreement among the Company and the
           persons named therein (incorporated by reference to Exhibit
           10.4 of the Form 8-B).
10.4.1     Amendment No. 1 to the Miscellaneous Rights Agreement
           (incorporated by reference to Exhibit 10.4.1 of the
           Quarterly Report on Form 10-Q of the Company and the
           Operating Partnership for the quarter ended September 30,
           1997 (the "1997 Third Quarter Form 10-Q")).
10.4.2     Amendment No. 2 to the Miscellaneous Rights Agreement
           (incorporated by reference to Exhibit 10.4.2 of the 1997
           Form 10-K).
10.5       Administrative Services Agreement (incorporated by reference
           to Exhibit 10.5 of the 1993 Form 10-K).
10.5.1     Amendment and Extension to the Administrative Services
           Agreement (incorporated by reference to Exhibit 10.5.1 of
           the Annual Report on Form 10-K of the Company for the year
           ended December 31, 1994).
10.5.4     Amendment No. 4 to the Administrative Services Agreement
           (incorporated by reference to Exhibit 10.5.4 of the
           Quarterly Report on Form 10-Q of the Company, the Operating
           Partnership and the Trust for the quarter ended June 30,
           1998 (the "1998 Second Quarter Form 10-Q")).
10.6       Exclusive Land Rights and Non-Competition Agreement
           (incorporated by reference to Exhibit 10.6 of the 1993 Form
           10-K).
10.6.1     Amendment No. 1 to the Exclusive Land Rights and
           Non-Competition Agreement (incorporated by reference to
           Exhibit 10.6.1 of the Quarterly Report on Form 10-Q of the
           Company for the quarter ended June 30, 1995 (the "1995
           Second Quarter Form 10-Q")).
10.6.2     Amendment No. 2 to the Exclusive Land Rights and
           Non-Competition Agreement (incorporated by reference to
           Exhibit 10.6.2 of the 1995 Second Quarter Form 10-Q).
10.6.3     Amendment No. 3 to the Exclusive Land Rights and
           Non-Competition Agreement (incorporated by reference to
           Exhibit 10.6.3 of the Form 8-B).
10.6.4     Amendment No. 4 to the Exclusive Land Rights and
           Non-Competition Agreement (incorporated by reference to
           Exhibit 10.6.4 of the 1997 Third Quarter Form 10-Q).
</TABLE>
<PAGE>   6
 
<TABLE>
<CAPTION>
EXHIBIT
NUMBER                             DESCRIPTION
-------                            -----------
<S>        <C>
10.6.5     Amendment No. 5 to the Exclusive Land Rights and
           Non-Competition Agreement (incorporated by reference to
           Exhibit 10.6.5 of the 1997 Form 10-K).
10.7       Contribution Agreement and Escrow Instructions Agreement
           (incorporated by reference to Exhibit 10.7 of the 1993 Form
           10-K).
10.8       Irvine Apartment Communities, Inc. 1993 Stock Option Plan
           for Directors (incorporated by reference to Exhibit 10.8 of
           the 1993 Form 10-K).
10.8.1     Irvine Apartment Communities, Inc. Amended and Restated 1993
           Stock Option Plan for Directors (incorporated by reference
           to Exhibit 10.8.1 of the 1998 Second Quarter Form 10-Q).
10.9       Irvine Apartment Communities, Inc. 1993 Long-Term Stock
           Incentive Plan (incorporated by reference to Exhibit 10.9 of
           the 1993 Form 10-K).
10.10      Irrevocable Trust Agreement (incorporated by reference to
           Exhibit 10.10 of the 1993 Form 10-K).
10.11      Revolving Credit Agreement dated as of June 27, 1997
           (incorporated by reference to Exhibit 10.11 of the Quarterly
           Report on Form 10-Q of the Company and the Operating
           Partnership for the quarter ended June 30, 1997 (the "1997
           Second Quarter Form 10-Q")).
10.12      Indenture of Trust for Tax-Exempt Mortgage Bond Financing
           (incorporated by reference to Exhibit 10.13 of the 1995
           Second Quarter Form 10-Q).
10.13      Employment Agreement with Chief Executive Officer
           (incorporated by reference to Exhibit 10.13 of the 1997
           Second Quarter Form 10-Q).
10.14      Irvine Apartment Communities, Inc. 1996 Long-Term Stock
           Incentive Plan (incorporated by reference to Exhibit 10.14
           of the Form 8-B).
10.15      Employment Agreement with the Senior Vice President,
           President, Irvine Ranch Division (incorporated by reference
           to Exhibit 10.15 of the 1997 Form 10-K).
10.16      Stock Purchase Agreement dated as of February 1, 1999 among
           the Operating Partnership, as buyer, and William H.
           Thompson, Bruce Dorfman and Robert Hughes, as sellers (see
           Exhibit 2.4).
10.17      Irvine Apartment Management Company Partnership Agreement
           dated March 12, 1998 by and between Apartment Management
           Company, LLC and Western National Securities d/b/a Western
           National Property Management ("WNPM") (incorporated by
           reference to Exhibit 10.17 of the Quarterly Report on Form
           10-Q of the Company, the Operating Partnership and the Trust
           for the quarter ended March 31, 1998 (the "1998 First
           Quarter Form 10-Q")).
10.18      Management Agreement dated as of April 1, 1998 by and
           between the Operating Partnership and Irvine Apartment
           Management Company (incorporated by reference to Exhibit
           10.18 of the 1998 First Quarter Form 10-Q).
10.19      Guaranty dated as of March 12, 1998 by the Operating
           Partnership in favor of WNPM and the WNPM Indemnities (as
           defined in Exhibit 10.17 hereto) (incorporated by reference
           to Exhibit 10.19 of the 1998 First Quarter Form 10-Q).
10.20      Irvine Apartment Communities, Inc. Deferred Compensation
           Plan for Outside Directors (incorporated by reference to
           Exhibit 10.20 of the 1998 Second Quarter Form 10-Q).
10.21      Letter Agreement dated February 1, 1999 from The Irvine
           Company to the Company.*
10.22      Unsecured Loan Agreement dated as of November 20, 1998 by
           and among the Operating Partnership, the Banks listed
           therein, Wells Fargo Bank, N.A., as Co-Arranger and
           Administrative Agent, and U.S. Bank National Association, as
           Co-Arranger.*
10.23.1    Retention Agreement with Mr. McFarland dated January 22,
           1999.*
10.23.2    Form of Retention Agreement with certain of the Company's
           executive officers.*
</TABLE>
<PAGE>   7
 
<TABLE>
<CAPTION>
EXHIBIT
NUMBER                             DESCRIPTION
-------                            -----------
<S>        <C>
10.23.3    Form of Retention Agreement with holders of awards under the
           1993 Long-Term Stock Incentive Plan or the 1996 Long-Term
           Stock Incentive Plan.*
10.24      Loan Agreement by and between California Statewide
           Communities Development Authority and the Operating
           Partnership dated as of May 15, 1998.*
10.25      Indenture of Trust by and between California Statewide
           Communities Development Authority and U.S. Bank Trust
           National Association, as Trustee dated as of May 15, 1998
           securing $334,190,000 California Statewide Communities
           Development Authority Apartment Development Revenue
           Refunding Bonds, Series 1998A (Irvine Apartment Communities,
           L.P.).*
10.26      First Supplemental Indenture of Trust by and between
           California Statewide Communities Development Authority and
           U.S. Bank Trust National Association, as Trustee dated as of
           June 11, 1998 ($334,190,000 California Statewide Communities
           Development Authority Apartment Development Revenue
           Refunding Bonds, Series 1995A).*
10.27      Registration Rights Agreement dated as of November 12, 1998
           by and among the Operating Partnership, the Company, the
           Trust and Greene Street 1998 Exchange Fund, L.P.*
12         The Company's ratio of earnings to fixed charges for the
           year ended December 31, 1998.*
21.1       Subsidiaries of the Company (incorporated by reference to
           Exhibit 21.1 of the 1997 Form 10-K).
21.2       Subsidiaries of the Operating Partnership (incorporated by
           reference to Exhibit 21.2 of the 1997 Form 10-K).
21.3       Subsidiaries of the Trust (none).
23.1       Consent of Ernst & Young LLP (with respect to Irvine
           Apartment Communities, Inc.).
23.2       Consent of Ernst & Young LLP (with respect to Irvine
           Apartment Communities, L.P.).
23.3       Consent of Ernst & Young LLP (with respect to IAC Capital
           Trust).
27.1       Financial Data Schedule for the Company (only included in
           electronically-filed document).*
27.2       Financial Data Schedule for the Operating Partnership (only
           included in electronically-filed document).*
27.3       Financial Data Schedule for IAC Capital Trust (only included
           in electronically-filed document).*
</TABLE>
 
---------------
 
   
 *  Filed with initial filing of this Report.