| Population Change 1990-2000 | ||||
| County or Municipality | 2000 Population | 1990 Population | Population Change | Percent Change |
| Pennsylvania | 12 281 054 | 11 881 643 | 399 411 | 3.4 |
| Delaware County | 550 864 | 547 651 | 3 213 | 0.6 |
| Aldan borough | 4 313 | 4 549 | - 236 | - 5.2 |
| Aston township | 16 203 | 15 080 | 1 123 | 7.4 |
| Bethel township | 6 421 | 3 330 | 3 091 | 92.8 |
| Brookhaven borough | 7 985 | 8 567 | - 582 | - 6.8 |
| Chadds Ford borough | 3 170 | 3 118 | 52 | 1.7 |
| Chester city | 36 854 | 41 856 | - 5 002 | - 12.0 |
| Chester township | 4 604 | 5 399 | - 795 | - 14.7 |
| Chester Heights borough | 2 481 | 2 273 | 208 | 9.2 |
| Clifton Heights borough | 6 779 | 7 111 | - 332 | - 4.7 |
| Collingdale borough | 8 664 | 9 175 | - 511 | - 5.6 |
| Colwyn borough | 2 453 | 2 613 | - 160 | - 6.1 |
| Concord township | 9 933 | 6 933 | 3 000 | 43.3 |
| Darby borough | 10 299 | 11 140 | - 841 | - 7.5 |
| Darby township | 9 622 | 10 955 | - 1 333 | - 12.2 |
| East Lansdowne borough | 2 586 | 2 691 | - 105 | - 3.9 |
| Eddystone borough | 2 442 | 2 446 | - 4 | - 0.2 |
| Edgmont township | 3 918 | 2 735 | 1 183 | 43.3 |
| Folcroft borough | 6 978 | 7 506 | - 528 | - 7.0 |
| Glenolden borough | 7 476 | 7 260 | 216 | 3.0 |
| Haverford township | 48 498 | 49 848 | - 1 350 | - 2.7 |
| Lansdowne borough | 11 044 | 11 712 | - 668 | - 5.7 |
| Lower Chichester township | 3 591 | 3 660 | - 69 | - 1.9 |
| Marcus Hook borough | 2 314 | 2 546 | - 232 | - 9.1 |
| Marple township | 23 737 | 23 123 | 614 | 2.7 |
| Media borough | 5 533 | 5 957 | - 424 | - 7.1 |
| Middletown township | 16 064 | 14 130 | 1 934 | 13.7 |
| Millbourne borough | 943 | 831 | 112 | 13.5 |
| Morton borough | 2 715 | 2 851 | - 136 | - 4.8 |
| Nether Providence township | 13 456 | 13 229 | 227 | 1.7 |
| Newtown township | 11 700 | 11 366 | 334 | 2.9 |
| Norwood borough | 5 985 | 6 162 | - 177 | - 2.9 |
| Parkside borough | 2 267 | 2 369 | - 102 | - 4.3 |
| Prospect Park borough | 6 594 | 6 764 | - 170 | - 2.5 |
| Radnor township | 30 878 | 28 703 | 2 175 | 7.6 |
| Ridley township | 30 791 | 31 169 | - 378 | - 1.2 |
| Ridley Park borough | 7 196 | 7 592 | - 396 | - 5.2 |
| Rose Valley borough | 944 | 982 | - 38 | - 3.9 |
| Rutledge borough | 860 | 843 | 17 | 2.0 |
| Sharon Hill borough | 5 468 | 5 771 | - 303 | - 5.3 |
| Springfield township | 23 677 | 24 160 | - 483 | - 2.0 |
| Swarthmore borough | 6 170 | 6 157 | 13 | 0.2 |
| Thornbury township | 7 093 | 5 056 | 2 037 | 40.3 |
| Tinicum township | 4 353 | 4 440 | - 87 | - 2.0 |
| Trainer borough | 1 901 | 2 271 | - 370 | - 16.3 |
| Upland borough | 2 977 | 3 334 | - 357 | - 10.7 |
| Upper Chichester township | 16 842 | 15 004 | 1 838 | 12.3 |
| Upper Darby township | 81 821 | 81 177 | 644 | 0.8 |
| Upper Providence township | 10 509 | 9 727 | 782 | 8.0 |
| Yeadon borough | 11 762 | 11 980 | - 218 | - 1.8 |
| Source: U.S. Census Bureau | Prepared by: Pennsylvania State Data Center | |||