41 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Edison | 1 | 113,208 | 107,061 | 1.44% | 3,764 | 30 | Township |
| Woodbridge | 2 | 108,905 | 103,664 | 1.3% | 4,682 | 23 | Township |
| Old Bridge | 3 | 73,162 | 66,753 | 1.85% | 1,916 | 38 | Township |
| Piscataway | 4 | 64,701 | 60,755 | 1.54% | 3,443 | 19 | Township |
| New Brunswick | 5 | 59,327 | 55,298 | 1.58% | 11,337 | 5 | City |
| Perth Amboy | 6 | 58,721 | 55,376 | 1.54% | 12,596 | 5 | City |
| New Brunswick | 7 | 58,581 | 55,298 | 0.94% | 11,195 | 5 | City |
| Perth Amboy | 8 | 57,720 | 55,376 | 0.68% | 12,381 | 5 | City |
| East Brunswick | 9 | 52,908 | 49,560 | 1.75% | 2,429 | 22 | Township |
| Monroe | 10 | 51,781 | 48,556 | 1.59% | 1,235 | 42 | Township |
| Sayreville | 11 | 49,189 | 45,213 | 2.1% | 3,107 | 16 | Borough |
| South Brunswick | 12 | 49,176 | 46,901 | 1.32% | 1,211 | 41 | Township |
| Sayreville | 13 | 48,141 | 45,213 | 1.02% | 3,041 | 16 | Borough |
| North Brunswick | 14 | 46,507 | 43,767 | 1.29% | 3,865 | 12 | Township |
| Carteret | 15 | 26,701 | 25,297 | 1.32% | 6,081 | 4 | Borough |
| Carteret | 16 | 26,356 | 25,297 | 0.68% | 6,002 | 4 | Borough |
| South Plainfield | 17 | 26,218 | 24,283 | 2.25% | 3,160 | 8 | Borough |
| South Plainfield | 18 | 25,451 | 24,283 | 0.77% | 3,068 | 8 | Borough |
| Plainsboro | 19 | 25,210 | 24,026 | 1.31% | 2,143 | 12 | Township |
| North Plainfield | 20 | 23,233 | 22,749 | 0.35% | 8,277 | 3 | Borough |
| South River | 21 | 16,848 | 16,050 | 1.37% | 6,050 | 3 | Borough |
| South River | 22 | 16,563 | 16,050 | 0.52% | 5,947 | 3 | Borough |
| Metuchen | 23 | 16,002 | 15,055 | 1.69% | 5,640 | 3 | Borough |
| Highland Park | 24 | 15,798 | 15,034 | 1.32% | 8,675 | 2 | Borough |
| Metuchen | 25 | 15,677 | 15,055 | 0.67% | 5,526 | 3 | Borough |
| Highland Park | 26 | 15,562 | 15,034 | 0.57% | 8,546 | 2 | Borough |
| Middlesex | 27 | 15,278 | 14,591 | 1.34% | 4,380 | 3 | Borough |
| Middlesex | 28 | 15,015 | 14,591 | 0.48% | 4,305 | 3 | Borough |
| South Amboy | 29 | 11,138 | 9,370 | 2.72% | 7,242 | 2 | City |
| South Amboy | 30 | 10,887 | 9,370 | 1.58% | 7,079 | 2 | City |
| Dunellen | 31 | 8,807 | 7,618 | 2.3% | 8,293 | 1 | Borough |
| Dunellen | 32 | 8,637 | 7,618 | 1.33% | 8,133 | 1 | Borough |
| Spotswood | 33 | 8,528 | 8,123 | 1.32% | 3,687 | 2 | Borough |
| Spotswood | 34 | 8,397 | 8,123 | 0.55% | 3,630 | 2 | Borough |
| Milltown | 35 | 7,362 | 7,021 | 1.32% | 4,737 | 2 | Borough |
| Milltown | 36 | 7,244 | 7,021 | 0.51% | 4,662 | 2 | Borough |
| Jamesburg | 37 | 6,027 | 5,734 | 1.33% | 6,833 | 1 | Borough |
| Jamesburg | 38 | 5,936 | 5,734 | 0.58% | 6,730 | 1 | Borough |
| Cranbury | 39 | 4,466 | 3,903 | 3.43% | 336 | 13 | Township |
| Helmetta | 40 | 2,572 | 2,451 | 1.34% | 3,106 | 1 | Borough |
| Helmetta | 41 | 2,530 | 2,451 | 0.52% | 3,056 | 1 | Borough |
Edison is the largest city in Middlesex County, with a population of 113,208.
Helmetta is the smallest city in Middlesex County, with a population of 2,530.
There are 41 cities in Middlesex County, New Jersey.