54 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Washington township | 1 | 49,698 | 48,720 | 0.32% | 2,328 | 21.35 | Township |
| Washington township | 2 | 18,328 | 18,148 | 0.32% | 411 | 44.58 | Township |
| Phillipsburg | 3 | 15,397 | 15,224 | 0.23% | 4,825 | 3.19 | Town |
| Phillipsburg town | 4 | 15,388 | 15,224 | 0.2% | 4,822 | 3.19 | Town |
| Hackettstown town | 5 | 10,131 | 10,232 | 0.03% | 2,805 | 3.61 | Town |
| Hackettstown | 6 | 10,053 | 10,232 | -0.36% | 2,783 | 3.61 | Town |
| Lopatcong township | 7 | 9,503 | 8,788 | 0.38% | 1,299 | 7.32 | Township |
| Washington township | 8 | 9,309 | 9,267 | 0.25% | 3,152 | 2.95 | Township |
| Mansfield township | 9 | 7,970 | 7,772 | 0.59% | 269 | 29.59 | Township |
| Washington | 10 | 7,371 | 7,281 | 0.24% | 3,751 | 1.97 | Borough |
| Washington borough | 11 | 7,349 | 7,281 | 0.1% | 3,740 | 1.97 | Borough |
| Washington township | 12 | 6,938 | 6,494 | 1.15% | 386 | 17.96 | Township |
| Blairstown township | 13 | 5,785 | 5,698 | 0.24% | 194 | 29.89 | Township |
| Independence township | 14 | 5,549 | 5,459 | 0.27% | 280 | 19.83 | Township |
| Allamuchy township | 15 | 5,470 | 5,345 | 0.22% | 274 | 19.99 | Township |
| Panther Valley | 16 | 4,871 | 3,937 | 2.16% | 1,633 | 2.98 | CDP |
| White township | 17 | 4,764 | 4,602 | 0.63% | 174 | 27.37 | Township |
| Delaware township | 18 | 4,583 | 4,544 | 0.13% | 125 | 36.66 | Township |
| Pohatcong township | 19 | 3,298 | 3,240 | 0.33% | 247 | 13.37 | Township |
| Knowlton township | 20 | 2,944 | 2,887 | 0.31% | 119 | 24.72 | Township |
| Liberty township | 21 | 2,696 | 2,665 | 0.15% | 231 | 11.67 | Township |
| Belvidere | 22 | 2,548 | 2,517 | 0.24% | 1,758 | 1.45 | Town |
| Belvidere town | 23 | 2,548 | 2,517 | 0.24% | 1,758 | 1.45 | Town |
| Harmony township | 24 | 2,531 | 2,495 | 0.12% | 107 | 23.75 | Township |
| Oxford township | 25 | 2,480 | 2,441 | 0.32% | 416 | 5.96 | Township |
| Alpha | 26 | 2,362 | 2,326 | 0.3% | 1,405 | 1.68 | Borough |
| Alpha borough | 27 | 2,360 | 2,326 | 0.25% | 1,404 | 1.68 | Borough |
| Frelinghuysen township | 28 | 2,236 | 2,197 | 0.27% | 95 | 23.62 | Township |
| Hope township | 29 | 1,863 | 1,832 | 0.32% | 103 | 18.09 | Township |
| Upper Pohatcong | 30 | 1,771 | 1,774 | -0.06% | 2,741 | 0.65 | CDP |
| Hardwick township | 31 | 1,612 | 1,593 | 0.06% | 43 | 37.52 | Township |
| Oxford | 32 | 1,289 | 1,285 | 1.02% | 1,868 | 0.69 | CDP |
| Brookfield | 33 | 799 | 956 | 1.14% | 959 | 0.83 | CDP |
| Washington township | 34 | 719 | 690 | 1.13% | 7 | 101.66 | Township |
| Lopatcong Overlook | 35 | 714 | 740 | -0.14% | 1,935 | 0.37 | CDP |
| Vienna | 36 | 712 | 1,018 | -2.47% | 244 | 2.92 | CDP |
| Stewartsville | 37 | 683 | 549 | 3.48% | 631 | 1.08 | CDP |
| Johnsonburg | 38 | 562 | 363 | 5.64% | 528 | 1.06 | CDP |
| Mountain Lake | 39 | 535 | 565 | -0.56% | 475 | 1.13 | CDP |
| Upper Stewartsville | 40 | 377 | 380 | 3.01% | 1,077 | 0.35 | CDP |
| Finesville | 41 | 370 | 272 | 3.64% | 175 | 2.12 | CDP |
| Hainesburg | 42 | 321 | 117 | 7% | 214 | 1.50 | CDP |
| Great Meadows | 43 | 312 | 264 | 0.32% | 204 | 1.53 | CDP |
| Harmony | 44 | 301 | 410 | -2.9% | 291 | 1.04 | CDP |
| Bridgeville | 45 | 295 | 311 | 4.61% | 325 | 0.91 | CDP |
| Delaware Park | 46 | 255 | 331 | -10.53% | 1,041 | 0.24 | CDP |
| Hope | 47 | 225 | 153 | 0.9% | 310 | 0.72 | CDP |
| Blairstown | 48 | 205 | 268 | -9.29% | 489 | 0.42 | CDP |
| Columbia | 49 | 204 | 143 | -0.97% | 2,040 | 0.10 | CDP |
| Brainards | 50 | 157 | 189 | -1.88% | 853 | 0.18 | CDP |
| Allamuchy | 51 | 128 | 114 | 7.56% | 50 | 2.58 | CDP |
| Delaware | 52 | 119 | 130 | -1.65% | 229 | 0.52 | CDP |
| Hutchinson | 53 | 110 | 122 | -1.79% | 112 | 0.98 | CDP |
| Buttzville | 54 | 92 | 57 | -4.17% | 112 | 0.82 | CDP |
Washington township is the largest city in Warren County, with a population of 49,698.
Buttzville is the smallest city in Warren County.
There are 54 cities in Warren County, New Jersey.