32 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hamilton township | 1 | 92,050 | 92,057 | 0.22% | 2,333 | 39.45 | Township |
| Trenton city | 2 | 89,790 | 90,592 | 0.09% | 11,805 | 7.61 | City |
| Trenton | 3 | 88,972 | 90,592 | -0.36% | 11,698 | 7.61 | City |
| Ewing township | 4 | 34,937 | 37,239 | 0.26% | 2,297 | 15.21 | Township |
| Lawrence township | 5 | 31,791 | 33,047 | 0.03% | 1,463 | 21.73 | Township |
| West Windsor township | 6 | 31,449 | 29,529 | 1.52% | 1,231 | 25.55 | Township |
| Princeton | 7 | 30,255 | 30,610 | -0.06% | 1,686 | 17.95 | Township |
| Princeton | 8 | 30,075 | 30,610 | -0.35% | 1,676 | 17.95 | Township |
| East Windsor township | 9 | 29,748 | 29,937 | -0.02% | 1,911 | 15.57 | Township |
| Hopewell township | 10 | 17,365 | 17,442 | -0.05% | 299 | 58.07 | Township |
| Princeton Meadows | 11 | 16,023 | 14,261 | 0.92% | 6,284 | 2.55 | CDP |
| Robbinsville township | 12 | 15,431 | 15,435 | 0.23% | 755 | 20.44 | Township |
| Mercerville | 13 | 14,648 | 12,783 | 0.65% | 3,972 | 3.69 | CDP |
| Hamilton Square | 14 | 11,672 | 11,526 | -0.63% | 2,730 | 4.28 | CDP |
| Twin Rivers | 15 | 8,319 | 7,221 | 0.7% | 6,587 | 1.26 | CDP |
| Heathcote | 16 | 7,011 | 7,389 | 1.14% | 2,236 | 3.13 | CDP |
| Hightstown borough | 17 | 5,855 | 5,883 | 0.02% | 4,749 | 1.23 | Borough |
| Hightstown | 18 | 5,833 | 5,883 | -0.17% | 4,731 | 1.23 | Borough |
| The College New Jersey | 19 | 5,374 | 3,864 | 7.14% | 12,556 | 0.43 | CDP |
| Hopewell township | 20 | 4,363 | 4,377 | 0.11% | 146 | 29.89 | Township |
| Robbinsville Center | 21 | 4,044 | 2,978 | 7.15% | 6,309 | 0.64 | CDP |
| Lawrenceville | 22 | 3,727 | 3,515 | -0.29% | 3,577 | 1.04 | CDP |
| Pennington borough | 23 | 2,890 | 2,796 | 0.87% | 3,007 | 0.96 | Borough |
| Pennington | 24 | 2,869 | 2,796 | 0.53% | 2,985 | 0.96 | Borough |
| Ten Mile Run | 25 | 2,312 | 1,801 | 1.05% | 911 | 2.54 | CDP |
| Princeton Junction | 26 | 1,911 | 1,989 | -1.9% | 1,048 | 1.82 | CDP |
| Hopewell borough | 27 | 1,894 | 1,899 | 0% | 2,616 | 0.72 | Borough |
| Hopewell | 28 | 1,890 | 1,899 | -0.11% | 2,610 | 0.72 | Borough |
| Griggstown | 29 | 1,173 | 858 | 2.09% | 480 | 2.44 | CDP |
| Titusville | 30 | 839 | 817 | 7.15% | 1,793 | 0.47 | CDP |
| Windsor | 31 | 410 | 618 | 7.05% | 357 | 1.15 | CDP |
| East Rocky Hill | 32 | 397 | 335 | -1% | 95 | 4.17 | CDP |
Hamilton township is the largest city in Mercer County, with a population of 92,050.
East Rocky Hill is the smallest city in Mercer County.
There are 32 cities in Mercer County, New Jersey.