27 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Franklin | 1 | 71,852 | 68,315 | 1.4% | 1,556 | 46 | Township |
| Vernon | 2 | 23,175 | 22,291 | 0.64% | 343 | 68 | Township |
| Sparta | 3 | 20,652 | 19,623 | 0.71% | 562 | 37 | Township |
| Franklin | 4 | 16,939 | 16,374 | 0.74% | 303 | 56 | Township |
| Hopatcong | 5 | 14,970 | 14,330 | 0.74% | 1,376 | 11 | Borough |
| Wantage | 6 | 11,261 | 10,788 | 0.78% | 169 | 67 | Township |
| Newton | 7 | 8,805 | 8,346 | 2.15% | 2,621 | 3 | Town |
| Hardyston | 8 | 8,578 | 8,114 | 0.62% | 269 | 32 | Township |
| Byram | 9 | 8,331 | 8,005 | 0.69% | 387 | 22 | Township |
| Andover | 10 | 5,777 | 5,995 | 0.8% | 288 | 20 | Township |
| Frankford | 11 | 5,415 | 5,296 | 0.61% | 160 | 34 | Township |
| Franklin | 12 | 5,145 | 4,896 | 0.84% | 1,181 | 4 | Borough |
| Stillwater | 13 | 4,145 | 3,990 | 0.63% | 154 | 27 | Township |
| Montague | 14 | 3,932 | 3,778 | 0.67% | 87 | 45 | Township |
| Green | 15 | 3,764 | 3,605 | 0.7% | 235 | 16 | Township |
| Stanhope | 16 | 3,645 | 3,515 | 0.64% | 1,983 | 2 | Borough |
| Hamburg | 17 | 3,393 | 3,258 | 0.62% | 2,963 | 1 | Borough |
| Fredon | 18 | 3,358 | 3,230 | 0.63% | 190 | 18 | Township |
| Franklin | 19 | 3,321 | 3,256 | 0.21% | 144 | 23 | Township |
| Franklin | 20 | 3,049 | 2,967 | 0.46% | 130 | 23 | Township |
| Lafayette | 21 | 2,473 | 2,349 | 0.9% | 138 | 18 | Township |
| Ogdensburg | 22 | 2,338 | 2,252 | 0.6% | 1,061 | 2 | Borough |
| Sussex | 23 | 2,098 | 2,019 | 0.62% | 3,538 | 1 | Borough |
| Sandyston | 24 | 2,046 | 1,975 | 0.59% | 50 | 41 | Township |
| Branchville | 25 | 820 | 786 | 0.61% | 1,383 | 1 | Borough |
| Andover | 26 | 618 | 594 | 0.65% | 458 | 1 | Borough |
| Walpack | 27 | 7 | 7 | 0% | 0.00 | 24 | Township |
Franklin is the largest city in Sussex County, with a population of 71,852.
Walpack is the smallest city in Sussex County, with a population of 7.
There are 27 cities in Sussex County, New Jersey.