18 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hamilton | 1 | 94,962 | 92,048 | 1.12% | 2,407 | 39 | Township |
| Trenton | 2 | 92,003 | 90,546 | 0.89% | 12,096 | 8 | City |
| Trenton | 3 | 91,354 | 90,546 | 0.18% | 12,011 | 8 | City |
| Ewing | 4 | 36,468 | 37,290 | 1.7% | 2,398 | 15 | Township |
| West Windsor | 5 | 33,559 | 29,530 | 4.09% | 1,314 | 26 | Township |
| Lawrence | 6 | 32,587 | 33,053 | 0.61% | 1,500 | 22 | Township |
| Princeton | 7 | 32,260 | 30,629 | 2.59% | 1,798 | 18 | Township |
| Princeton | 8 | 31,649 | 30,629 | 0.65% | 1,764 | 18 | Township |
| East Windsor | 9 | 30,710 | 29,941 | 0.9% | 1,973 | 16 | Township |
| Hopewell | 10 | 18,223 | 17,442 | 1.71% | 314 | 58 | Township |
| Robbinsville | 11 | 16,280 | 15,442 | 2.21% | 796 | 20 | Township |
| Hightstown | 12 | 6,028 | 5,884 | 0.84% | 4,889 | 1 | Borough |
| Hightstown | 13 | 6,001 | 5,884 | 0.38% | 4,867 | 1 | Borough |
| Hopewell | 14 | 4,521 | 4,377 | 1.55% | 151 | 30 | Township |
| Pennington | 15 | 2,945 | 2,787 | 1.34% | 3,065 | 1 | Borough |
| Pennington | 16 | 2,935 | 2,787 | 1% | 3,054 | 1 | Borough |
| Hopewell | 17 | 1,955 | 1,900 | 0.88% | 2,700 | 1 | Borough |
| Hopewell | 18 | 1,947 | 1,900 | 0.46% | 2,689 | 1 | Borough |
Hamilton is the largest city in Mercer County, with a population of 94,962.
Hopewell is the smallest city in Mercer County, with a population of 1,947.
There are 18 cities in Mercer County, New Jersey.