41 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Edison | 1 | 111,605 | 107,061 | 1.46% | 3,710 | 30 | Township |
| Woodbridge | 2 | 107,503 | 103,664 | 1.32% | 4,622 | 23 | Township |
| Old Bridge | 3 | 71,834 | 66,753 | 1.88% | 1,881 | 38 | Township |
| Piscataway | 4 | 63,717 | 60,755 | 1.57% | 3,390 | 19 | Township |
| New Brunswick | 5 | 58,407 | 55,298 | 1.6% | 11,161 | 5 | City |
| New Brunswick | 6 | 58,034 | 55,298 | 0.95% | 11,090 | 5 | City |
| Perth Amboy | 7 | 57,830 | 55,376 | 1.56% | 12,405 | 5 | City |
| Perth Amboy | 8 | 57,329 | 55,376 | 0.68% | 12,297 | 5 | City |
| East Brunswick | 9 | 51,997 | 49,560 | 1.78% | 2,387 | 22 | Township |
| Monroe | 10 | 50,969 | 48,556 | 1.62% | 1,215 | 42 | Township |
| South Brunswick | 11 | 48,536 | 46,901 | 1.34% | 1,195 | 41 | Township |
| Sayreville | 12 | 48,177 | 45,213 | 2.15% | 3,043 | 16 | Borough |
| Sayreville | 13 | 47,653 | 45,213 | 1.03% | 3,010 | 16 | Borough |
| North Brunswick | 14 | 45,915 | 43,767 | 1.31% | 3,816 | 12 | Township |
| Carteret | 15 | 26,352 | 25,297 | 1.34% | 6,001 | 4 | Borough |
| Carteret | 16 | 26,179 | 25,297 | 0.68% | 5,962 | 4 | Borough |
| South Plainfield | 17 | 25,640 | 24,283 | 2.31% | 3,091 | 8 | Borough |
| South Plainfield | 18 | 25,256 | 24,283 | 0.77% | 3,044 | 8 | Borough |
| Plainsboro | 19 | 24,884 | 24,026 | 1.33% | 2,115 | 12 | Township |
| North Plainfield | 20 | 23,152 | 22,749 | 0.35% | 8,248 | 3 | Borough |
| South River | 21 | 16,620 | 16,050 | 1.39% | 5,968 | 3 | Borough |
| South River | 22 | 16,477 | 16,050 | 0.52% | 5,916 | 3 | Borough |
| Metuchen | 23 | 15,736 | 15,055 | 1.72% | 5,547 | 3 | Borough |
| Highland Park | 24 | 15,592 | 15,034 | 1.34% | 8,562 | 2 | Borough |
| Metuchen | 25 | 15,573 | 15,055 | 0.67% | 5,489 | 3 | Borough |
| Highland Park | 26 | 15,474 | 15,034 | 0.57% | 8,498 | 2 | Borough |
| Middlesex | 27 | 15,076 | 14,591 | 1.36% | 4,322 | 3 | Borough |
| Middlesex | 28 | 14,944 | 14,591 | 0.47% | 4,284 | 3 | Borough |
| South Amboy | 29 | 10,843 | 9,370 | 2.79% | 7,050 | 2 | City |
| South Amboy | 30 | 10,718 | 9,370 | 1.6% | 6,969 | 2 | City |
| Dunellen | 31 | 8,609 | 7,618 | 2.35% | 8,106 | 1 | Borough |
| Dunellen | 32 | 8,524 | 7,618 | 1.34% | 8,026 | 1 | Borough |
| Spotswood | 33 | 8,417 | 8,123 | 1.34% | 3,639 | 2 | Borough |
| Spotswood | 34 | 8,351 | 8,123 | 0.54% | 3,610 | 2 | Borough |
| Milltown | 35 | 7,266 | 7,021 | 1.34% | 4,676 | 2 | Borough |
| Milltown | 36 | 7,207 | 7,021 | 0.52% | 4,638 | 2 | Borough |
| Jamesburg | 37 | 5,948 | 5,734 | 1.35% | 6,744 | 1 | Borough |
| Jamesburg | 38 | 5,902 | 5,734 | 0.56% | 6,692 | 1 | Borough |
| Cranbury | 39 | 4,318 | 3,903 | 3.55% | 325 | 13 | Township |
| Helmetta | 40 | 2,538 | 2,451 | 1.36% | 3,065 | 1 | Borough |
| Helmetta | 41 | 2,517 | 2,451 | 0.52% | 3,040 | 1 | Borough |
Edison is the largest city in Middlesex County, with a population of 111,605.
Helmetta is the smallest city in Middlesex County, with a population of 2,517.
There are 41 cities in Middlesex County, New Jersey.