47 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Franklin | 1 | 70,857 | 68,315 | 1.42% | 1,535 | 46 | Township |
| Vernon | 2 | 23,027 | 22,291 | 0.65% | 341 | 68 | Township |
| Sparta | 3 | 20,507 | 19,623 | 0.71% | 558 | 37 | Township |
| Franklin | 4 | 16,815 | 16,374 | 0.74% | 301 | 56 | Township |
| Hopatcong | 5 | 14,860 | 14,330 | 0.75% | 1,366 | 11 | Borough |
| Hopatcong | 6 | 14,855 | 14,330 | 0.71% | 1,365 | 11 | Borough |
| Wantage | 7 | 11,174 | 10,788 | 0.78% | 167 | 67 | Township |
| Lake Mohawk | 8 | 9,650 | 9,148 | -0.19% | 1,922 | 5 | CDP |
| Newton | 9 | 8,620 | 8,346 | 2.19% | 2,565 | 3 | Town |
| Hardyston | 10 | 8,525 | 8,114 | 0.63% | 267 | 32 | Township |
| Newton | 11 | 8,457 | 8,346 | 0.26% | 2,517 | 3 | Town |
| Byram | 12 | 8,274 | 8,005 | 0.69% | 384 | 22 | Township |
| Andover | 13 | 5,731 | 5,995 | 0.81% | 286 | 20 | Township |
| Frankford | 14 | 5,382 | 5,296 | 0.62% | 159 | 34 | Township |
| Highland Lakes | 15 | 5,111 | 4,666 | 7.15% | 1,183 | 4 | CDP |
| Franklin | 16 | 5,102 | 4,896 | 0.85% | 1,171 | 4 | Borough |
| Franklin | 17 | 5,099 | 4,896 | 0.79% | 1,171 | 4 | Borough |
| Stillwater | 18 | 4,119 | 3,990 | 0.64% | 153 | 27 | Township |
| Montague | 19 | 3,906 | 3,778 | 0.67% | 86 | 45 | Township |
| Green | 20 | 3,738 | 3,605 | 0.7% | 233 | 16 | Township |
| Stanhope | 21 | 3,622 | 3,515 | 0.64% | 1,971 | 2 | Borough |
| Stanhope | 22 | 3,620 | 3,515 | 0.58% | 1,970 | 2 | Borough |
| Hamburg | 23 | 3,374 | 3,258 | 0.69% | 2,947 | 1 | Borough |
| Hamburg | 24 | 3,372 | 3,258 | 0.63% | 2,945 | 1 | Borough |
| Fredon | 25 | 3,337 | 3,230 | 0.63% | 189 | 18 | Township |
| Franklin | 26 | 3,314 | 3,256 | 0.21% | 144 | 23 | Township |
| Franklin | 27 | 3,035 | 2,967 | 0.46% | 130 | 23 | Township |
| Byram Center | 28 | 2,461 | 2,017 | 7.14% | 860 | 3 | CDP |
| Lafayette | 29 | 2,451 | 2,349 | 0.91% | 137 | 18 | Township |
| Ogdensburg | 30 | 2,324 | 2,252 | 0.61% | 1,054 | 2 | Borough |
| Ogdensburg | 31 | 2,324 | 2,252 | 0.61% | 1,054 | 2 | Borough |
| Sussex | 32 | 2,085 | 2,019 | 0.63% | 3,516 | 1 | Borough |
| Sussex | 33 | 2,085 | 2,019 | 0.63% | 3,516 | 1 | Borough |
| Sandyston | 34 | 2,034 | 1,975 | 0.59% | 49 | 41 | Township |
| Vernon Center | 35 | 1,438 | 1,462 | -1.24% | 488 | 3 | CDP |
| Layton | 36 | 1,248 | 928 | 7.22% | 179 | 7 | CDP |
| Crandon Lakes | 37 | 1,132 | 1,221 | -0.26% | 443 | 3 | CDP |
| Vernon Valley | 38 | 948 | 1,171 | -4.63% | 356 | 3 | CDP |
| Branchville | 39 | 816 | 786 | 0.74% | 1,376 | 1 | Borough |
| Branchville | 40 | 815 | 786 | 0.62% | 1,374 | 1 | Borough |
| Andover | 41 | 614 | 594 | 0.66% | 455 | 1 | Borough |
| Andover | 42 | 614 | 594 | 0.66% | 455 | 1 | Borough |
| Silver Lake | 43 | 313 | 397 | -1.26% | 248 | 1 | CDP |
| Mount Hermon | 44 | 252 | 163 | 2.86% | 270 | 1 | CDP |
| Marksboro | 45 | 206 | 125 | 7.29% | 96 | 2 | CDP |
| Ross Corner | 46 | 82 | 209 | 6.49% | 46 | 2 | CDP |
| Walpack | 47 | 7 | 7 | 0% | 0.00 | 24 | Township |
Franklin is the largest city in Sussex County, with a population of 70,857.
Walpack is the smallest city in Sussex County, with a population of 7.
There are 47 cities in Sussex County, New Jersey.