47 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Franklin township | 1 | 67,729 | 68,312 | -0.37% | 1,467 | 46.17 | Township |
| Vernon township | 2 | 22,929 | 22,296 | 0.48% | 340 | 67.52 | Township |
| Sparta township | 3 | 20,409 | 19,623 | 0.53% | 555 | 36.74 | Township |
| Franklin township | 4 | 16,699 | 16,371 | 0.47% | 299 | 55.83 | Township |
| Hopatcong | 5 | 14,818 | 14,328 | 0.67% | 1,362 | 10.88 | Borough |
| Hopatcong borough | 6 | 14,780 | 14,328 | 0.54% | 1,358 | 10.88 | Borough |
| Wantage township | 7 | 11,099 | 10,793 | 0.48% | 166 | 66.76 | Township |
| Lake Mohawk | 8 | 9,650 | 9,148 | -0.19% | 1,922 | 5.02 | CDP |
| Hardyston township | 9 | 8,591 | 8,112 | 1.07% | 269 | 31.93 | Township |
| Byram township | 10 | 8,222 | 8,005 | 0.43% | 382 | 21.53 | Township |
| Newton | 11 | 8,170 | 8,344 | -0.43% | 2,432 | 3.36 | Town |
| Newton town | 12 | 7,966 | 8,344 | -1.69% | 2,371 | 3.36 | Town |
| Andover township | 13 | 5,691 | 5,996 | 0.49% | 284 | 20.04 | Township |
| Frankford township | 14 | 5,278 | 5,291 | -0.25% | 156 | 33.88 | Township |
| Highland Lakes | 15 | 5,111 | 4,666 | 7.15% | 1,183 | 4.32 | CDP |
| Franklin borough | 16 | 5,094 | 4,894 | 0.85% | 1,169 | 4.36 | Borough |
| Franklin | 17 | 5,084 | 4,894 | 0.75% | 1,167 | 4.36 | Borough |
| Stillwater township | 18 | 4,091 | 3,990 | 0.34% | 152 | 26.92 | Township |
| Montague township | 19 | 3,898 | 3,779 | 0.62% | 86 | 45.23 | Township |
| Green township | 20 | 3,723 | 3,605 | 0.54% | 232 | 16.03 | Township |
| Stanhope | 21 | 3,613 | 3,517 | 0.53% | 1,966 | 1.84 | Borough |
| Stanhope borough | 22 | 3,609 | 3,517 | 0.47% | 1,964 | 1.84 | Borough |
| Hamburg | 23 | 3,376 | 3,263 | 0.69% | 2,948 | 1.15 | Borough |
| Hamburg borough | 24 | 3,373 | 3,263 | 0.63% | 2,946 | 1.15 | Borough |
| Fredon township | 25 | 3,323 | 3,231 | 0.45% | 188 | 17.64 | Township |
| Franklin township | 26 | 3,266 | 3,254 | -0.31% | 142 | 23.04 | Township |
| Franklin township | 27 | 3,014 | 2,965 | 0.23% | 129 | 23.42 | Township |
| Byram Center | 28 | 2,461 | 2,017 | 7.14% | 860 | 2.86 | CDP |
| Lafayette township | 29 | 2,432 | 2,345 | 0.66% | 136 | 17.88 | Township |
| Ogdensburg | 30 | 2,320 | 2,252 | 0.61% | 1,053 | 2.20 | Borough |
| Ogdensburg borough | 31 | 2,315 | 2,252 | 0.48% | 1,050 | 2.20 | Borough |
| Sussex | 32 | 2,074 | 2,014 | 0.58% | 3,497 | 0.59 | Borough |
| Sussex borough | 33 | 2,068 | 2,014 | 0.44% | 3,487 | 0.59 | Borough |
| Sandyston township | 34 | 2,026 | 1,974 | 0.5% | 49 | 41.30 | Township |
| Vernon Center | 35 | 1,438 | 1,462 | -1.24% | 488 | 2.95 | CDP |
| Layton | 36 | 1,248 | 928 | 7.22% | 179 | 6.98 | CDP |
| Crandon Lakes | 37 | 1,132 | 1,221 | -0.26% | 443 | 2.56 | CDP |
| Vernon Valley | 38 | 948 | 1,171 | -4.63% | 356 | 2.67 | CDP |
| Branchville | 39 | 820 | 789 | 0.74% | 1,383 | 0.59 | Borough |
| Branchville borough | 40 | 816 | 789 | 0.49% | 1,376 | 0.59 | Borough |
| Andover | 41 | 610 | 592 | 0.66% | 453 | 1.35 | Borough |
| Andover borough | 42 | 609 | 592 | 0.5% | 452 | 1.35 | Borough |
| Silver Lake | 43 | 313 | 397 | -1.26% | 248 | 1.26 | CDP |
| Mount Hermon | 44 | 252 | 163 | 2.86% | 270 | 0.93 | CDP |
| Marksboro | 45 | 206 | 125 | 7.29% | 96 | 2.15 | CDP |
| Ross Corner | 46 | 82 | 209 | 6.49% | 46 | 1.78 | CDP |
| Walpack township | 47 | 6 | 6 | 0% | 0.00 | 24.17 | Township |
Franklin township is the largest city in Sussex County, with a population of 67,729.
Walpack township is the smallest city in Sussex County.
There are 47 cities in Sussex County, New Jersey.