Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Edison township | 1 | 106,674 | 107,066 | -0.15% | 3,546 | 30.1 | Township |
| Woodbridge township | 2 | 103,181 | 103,656 | -0.01% | 4,436 | 23.3 | Township |
| Old Bridge township | 3 | 68,556 | 66,744 | 0.57% | 1,796 | 38.2 | Township |
| Piscataway township | 4 | 61,344 | 60,742 | 0.66% | 3,264 | 18.8 | Township |
| New Brunswick | 5 | 55,847 | 55,288 | 0% | 10,672 | 5.2 | City |
| Perth Amboy | 6 | 55,290 | 55,383 | 0.07% | 11,860 | 4.7 | City |
| East Brunswick township | 7 | 49,721 | 49,559 | 0.55% | 2,282 | 21.8 | Township |
| Monroe township | 8 | 48,853 | 48,493 | 0.59% | 1,165 | 41.9 | Township |
| South Brunswick township | 9 | 46,593 | 46,896 | 0.06% | 1,147 | 40.6 | Township |
| Sayreville borough | 10 | 45,853 | 45,225 | 0.78% | 2,897 | 15.8 | Borough |
| North Brunswick township | 11 | 44,144 | 43,774 | 0.08% | 3,669 | 12.0 | Township |
| Carteret borough | 12 | 25,457 | 25,297 | 0.7% | 5,798 | 4.4 | Borough |
| South Plainfield borough | 13 | 24,117 | 24,286 | -0.06% | 2,907 | 8.3 | Borough |
| Plainsboro township | 14 | 23,886 | 24,021 | 0.05% | 2,031 | 11.8 | Township |
| South River borough | 15 | 15,945 | 16,051 | 0.09% | 5,725 | 2.8 | Borough |
| Metuchen borough | 16 | 15,015 | 15,048 | 0.25% | 5,293 | 2.8 | Borough |
| Highland Park borough | 17 | 14,971 | 15,033 | 0.08% | 8,221 | 1.8 | Borough |
| Middlesex borough | 18 | 14,466 | 14,593 | 0.03% | 4,147 | 3.5 | Borough |
| South Amboy | 19 | 10,237 | 9,377 | 0% | 6,656 | 1.5 | City |
| Dunellen borough | 20 | 8,799 | 7,617 | 7.62% | 8,285 | 1.1 | Borough |
| Spotswood borough | 21 | 8,085 | 8,125 | 0.09% | 3,495 | 2.3 | Borough |
| Milltown borough | 22 | 6,974 | 7,018 | 0.09% | 4,488 | 1.6 | Borough |
| Jamesburg borough | 23 | 5,743 | 5,763 | 0.14% | 6,511 | 0.9 | Borough |
| Cranbury township | 24 | 3,962 | 3,899 | 0.05% | 298 | 13.3 | Township |
| Helmetta borough | 25 | 2,439 | 2,454 | 0.08% | 2,946 | 0.8 | Borough |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Edison township is the largest city in Middlesex County.
Helmetta borough is the smallest city in Middlesex County.
There are 25 cities in Middlesex County, New Jersey.