| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Edison | 1 | 109,132 | 107,024 | 0.05% | 3,628 | 30 | Township |
| Woodbridge | 2 | 104,499 | 103,661 | -0.29% | 4,493 | 23 | Township |
| Old Bridge | 3 | 70,634 | 66,739 | 0.58% | 1,850 | 38 | Township |
| Piscataway | 4 | 62,323 | 60,758 | 0.11% | 3,316 | 19 | Township |
| New Brunswick | 5 | 57,265 | 55,291 | 0.23% | 10,943 | 5 | City |
| Perth Amboy | 6 | 57,097 | 55,360 | 0.63% | 12,247 | 5 | City |
| East Brunswick | 7 | 50,780 | 49,524 | 0.2% | 2,331 | 22 | Township |
| Monroe | 8 | 49,998 | 48,485 | 0.34% | 1,192 | 42 | Township |
| South Brunswick | 9 | 47,485 | 46,901 | 0.07% | 1,169 | 41 | Township |
| Sayreville | 10 | 46,844 | 45,245 | 0.12% | 2,959 | 16 | Borough |
| North Brunswick | 11 | 45,314 | 43,763 | 0.48% | 3,766 | 12 | Township |
| Carteret | 12 | 25,816 | 25,296 | 0.14% | 5,879 | 4 | Borough |
| South Plainfield | 13 | 24,967 | 24,273 | 0.31% | 3,010 | 8 | Borough |
| Plainsboro | 14 | 24,383 | 24,022 | 0.14% | 2,073 | 12 | Township |
| South River | 15 | 16,282 | 16,062 | 0.12% | 5,846 | 3 | Borough |
| Metuchen | 16 | 15,412 | 15,052 | 0.32% | 5,432 | 3 | Borough |
| Highland Park | 17 | 15,282 | 15,035 | 0.15% | 8,392 | 2 | Borough |
| Middlesex | 18 | 14,752 | 14,591 | 0.08% | 4,229 | 3 | Borough |
| South Amboy | 19 | 10,428 | 9,337 | 0.24% | 6,780 | 2 | City |
| Dunellen | 20 | 8,349 | 7,616 | 0.14% | 7,862 | 1 | Borough |
| Spotswood | 21 | 8,248 | 8,123 | 0.15% | 3,566 | 2 | Borough |
| Milltown | 22 | 7,102 | 7,025 | -0.01% | 4,570 | 2 | Borough |
| Jamesburg | 23 | 5,827 | 5,734 | 0.14% | 6,607 | 1 | Borough |
| Cranbury | 24 | 4,352 | 3,890 | 2.64% | 328 | 13 | Township |
| Helmetta | 25 | 2,479 | 2,441 | 0.2% | 2,994 | 1 | Borough |
Edison is the largest city in Middlesex County, with a population of 109,132.
Helmetta is the smallest city in Middlesex County, with a population of 2,479.
There are 25 cities in Middlesex County, New Jersey.