Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Washington township | 1 | 49,538 | 48,720 | 0.32% | 2,321 | 21.3 | Township |
| Washington township | 2 | 18,270 | 18,148 | 0.32% | 410 | 44.6 | Township |
| Phillipsburg | 3 | 15,358 | 15,224 | 0.2% | 4,813 | 3.2 | Town |
| Hackettstown | 4 | 10,128 | 10,232 | 0.03% | 2,804 | 3.6 | Town |
| Lopatcong township | 5 | 9,467 | 8,788 | 0.38% | 1,294 | 7.3 | Township |
| Washington township | 6 | 9,286 | 9,267 | 0.25% | 3,145 | 3.0 | Township |
| Mansfield township | 7 | 7,923 | 7,772 | 0.6% | 268 | 29.6 | Township |
| Washington borough | 8 | 7,342 | 7,281 | 0.1% | 3,736 | 2.0 | Borough |
| Washington township | 9 | 6,859 | 6,494 | 1.17% | 382 | 18.0 | Township |
| Blairstown township | 10 | 5,771 | 5,698 | 0.24% | 193 | 29.9 | Township |
| Independence township | 11 | 5,534 | 5,459 | 0.27% | 279 | 19.8 | Township |
| Allamuchy township | 12 | 5,458 | 5,345 | 0.22% | 273 | 20.0 | Township |
| White township | 13 | 4,734 | 4,602 | 0.64% | 173 | 27.4 | Township |
| Delaware township | 14 | 4,577 | 4,544 | 0.13% | 125 | 36.7 | Township |
| Pohatcong township | 15 | 3,287 | 3,240 | 0.34% | 246 | 13.4 | Township |
| Knowlton township | 16 | 2,935 | 2,887 | 0.31% | 119 | 24.7 | Township |
| Liberty township | 17 | 2,692 | 2,665 | 0.15% | 231 | 11.7 | Township |
| Belvidere | 18 | 2,542 | 2,517 | 0.24% | 1,754 | 1.4 | Town |
| Harmony township | 19 | 2,528 | 2,495 | 0.12% | 106 | 23.8 | Township |
| Oxford township | 20 | 2,472 | 2,441 | 0.33% | 415 | 6.0 | Township |
| Alpha borough | 21 | 2,354 | 2,326 | 0.26% | 1,400 | 1.7 | Borough |
| Frelinghuysen township | 22 | 2,230 | 2,197 | 0.27% | 94 | 23.6 | Township |
| Hope township | 23 | 1,857 | 1,832 | 0.32% | 103 | 18.1 | Township |
| Hardwick township | 24 | 1,611 | 1,593 | 0.06% | 43 | 37.5 | Township |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Washington township is the largest city in Warren County.
Hardwick township is the smallest city in Warren County.
There are 24 cities in Warren County, New Jersey.