31 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Bridgewater | 1 | 47,499 | 45,878 | 1.34% | 1,490 | 32 | Township |
| Hillsborough | 2 | 46,290 | 43,242 | 1.91% | 848 | 55 | Township |
| Bernards | 3 | 29,077 | 27,769 | 1.25% | 1,201 | 24 | Township |
| Raritan | 4 | 25,848 | 23,532 | 2.21% | 690 | 37 | Township |
| Montgomery | 5 | 24,569 | 23,635 | 1.3% | 761 | 32 | Township |
| North Plainfield | 6 | 23,366 | 22,749 | 1.27% | 8,324 | 3 | Borough |
| Warren | 7 | 17,332 | 15,886 | 3.05% | 886 | 20 | Township |
| Branchburg | 8 | 15,849 | 14,900 | 1.47% | 790 | 20 | Township |
| Somerville | 9 | 14,945 | 12,357 | 3.58% | 6,392 | 2 | Borough |
| Somerville | 10 | 14,615 | 12,357 | 1.3% | 6,251 | 2 | Borough |
| Bound Brook | 11 | 12,815 | 11,952 | 1.36% | 7,715 | 2 | Borough |
| Bound Brook | 12 | 12,803 | 11,952 | 1.27% | 7,708 | 2 | Borough |
| Manville | 13 | 11,180 | 10,932 | 1.35% | 4,735 | 2 | Borough |
| Manville | 14 | 11,055 | 10,932 | 0.22% | 4,682 | 2 | Borough |
| Raritan | 15 | 8,775 | 7,820 | 2.23% | 4,405 | 2 | Borough |
| Raritan | 16 | 8,668 | 7,820 | 0.98% | 4,351 | 2 | Borough |
| Bedminster | 17 | 8,458 | 8,250 | 1.22% | 324 | 26 | Township |
| Bernardsville | 18 | 8,130 | 7,881 | 1.37% | 633 | 13 | Borough |
| Bernardsville | 19 | 8,054 | 7,881 | 0.42% | 627 | 13 | Borough |
| Green Brook | 20 | 7,541 | 7,262 | 1.21% | 1,711 | 4 | Township |
| Watchung | 21 | 6,715 | 6,443 | 1.65% | 1,116 | 6 | Borough |
| Watchung | 22 | 6,646 | 6,443 | 0.61% | 1,105 | 6 | Borough |
| South Bound Brook | 23 | 5,073 | 4,853 | 2.18% | 7,865 | 1 | Borough |
| South Bound Brook | 24 | 4,993 | 4,853 | 0.56% | 7,741 | 1 | Borough |
| Peapack and Gladstone | 25 | 2,645 | 2,553 | 1.65% | 461 | 6 | Borough |
| Far Hills | 26 | 947 | 922 | 1.28% | 195 | 5 | Borough |
| Far Hills | 27 | 938 | 922 | 0.32% | 194 | 5 | Borough |
| Rocky Hill | 28 | 764 | 740 | 1.19% | 1,252 | 1 | Borough |
| Rocky Hill | 29 | 758 | 740 | 0.4% | 1,243 | 1 | Borough |
| Millstone | 30 | 461 | 449 | 1.32% | 677 | 1 | Borough |
| Millstone | 31 | 456 | 449 | 0.22% | 670 | 1 | Borough |
Bridgewater is the largest city in Somerset County, with a population of 47,499.
Millstone is the smallest city in Somerset County, with a population of 456.
There are 31 cities in Somerset County, New Jersey.