<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 9
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM DIME BANCORP
INC.'S FORM 10-Q FOR THE QUARTERLY PERIOD ENDED SEPTEMBER 30, 1997 AND IS
QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1997
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               SEP-30-1997
<CASH>                                         172,879
<INT-BEARING-DEPOSITS>                           4,932
<FED-FUNDS-SOLD>                                18,885
<TRADING-ASSETS>                                     0
<INVESTMENTS-HELD-FOR-SALE>                  1,787,279
<INVESTMENTS-CARRYING>                       3,765,766
<INVESTMENTS-MARKET>                         3,709,365
<LOANS>                                     12,643,266
<ALLOWANCE>                                    102,061
<TOTAL-ASSETS>                              19,413,597
<DEPOSITS>                                  13,392,320
<SHORT-TERM>                                 3,534,354
<LIABILITIES-OTHER>                            172,724
<LONG-TERM>                                  1,261,195
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                         1,083
<OTHER-SE>                                   1,051,921
<TOTAL-LIABILITIES-AND-EQUITY>              19,413,597
<INTEREST-LOAN>                                651,935
<INTEREST-INVEST>                              337,404
<INTEREST-OTHER>                                25,370
<INTEREST-TOTAL>                             1,014,709
<INTEREST-DEPOSIT>                             415,230
<INTEREST-EXPENSE>                             658,172
<INTEREST-INCOME-NET>                          356,537
<LOAN-LOSSES>                                   41,000
<SECURITIES-GAINS>                               7,166
<EXPENSE-OTHER>                                240,352
<INCOME-PRETAX>                                162,306
<INCOME-PRE-EXTRAORDINARY>                     162,306
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                   100,215
<EPS-PRIMARY>                                     0.95
<EPS-DILUTED>                                     0.95
<YIELD-ACTUAL>                                    2.52
<LOANS-NON>                                     95,171
<LOANS-PAST>                                         0
<LOANS-TROUBLED>                                85,384
<LOANS-PROBLEM>                                      0
<ALLOWANCE-OPEN>                               106,495
<CHARGE-OFFS>                                   65,102
<RECOVERIES>                                     6,419
<ALLOWANCE-CLOSE>                              102,061
<ALLOWANCE-DOMESTIC>                           102,061
<ALLOWANCE-FOREIGN>                                  0
<ALLOWANCE-UNALLOCATED>                              0
        

</TABLE>