City | Rank | 2026 Pop.↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Troy | 1 | 50,787 | 51,176 | -0.25% | 4,904 | 10 | City |
| East Greenbush | 2 | 16,549 | 16,811 | -0.07% | 689 | 24 | Town |
| North Greenbush | 3 | 13,649 | 13,295 | 0.93% | 736 | 19 | Town |
| Schodack | 4 | 12,913 | 12,937 | 0.16% | 209 | 62 | Town |
| Brunswick | 5 | 12,641 | 12,733 | 0.12% | 285 | 44 | Town |
| Rensselaer | 6 | 9,471 | 9,208 | 0.53% | 2,979 | 3 | City |
| Sand Lake | 7 | 8,382 | 8,336 | 0.4% | 239 | 35 | Town |
| Schaghticoke | 8 | 7,285 | 7,396 | -0.16% | 146 | 50 | Town |
| Hoosick | 9 | 6,685 | 6,704 | 0.1% | 106 | 63 | Town |
| Pittstown | 10 | 5,505 | 5,528 | 0.6% | 89 | 62 | Town |
| Nassau | 11 | 4,497 | 4,542 | 0.18% | 101 | 44 | Town |
| Poestenkill | 12 | 4,360 | 4,311 | 0.32% | 135 | 32 | Town |
| Hoosick Falls | 13 | 3,163 | 3,203 | -0.25% | 1,979 | 2 | Village |
| Stephentown | 14 | 2,783 | 2,787 | 0.04% | 48 | 58 | Town |
| Grafton | 15 | 2,109 | 2,052 | 0.52% | 47 | 45 | Town |
| Berlin | 16 | 1,696 | 1,700 | 0.06% | 28 | 60 | Town |
| Castleton-on-Hudson | 17 | 1,460 | 1,471 | -0.21% | 2,045 | 1 | Village |
| Petersburgh | 18 | 1,370 | 1,373 | 0.07% | 33 | 42 | Town |
| Nassau | 19 | 1,072 | 1,098 | -0.46% | 1,534 | 1 | Village |
| Schaghticoke | 20 | 544 | 558 | -0.55% | 718 | 1 | Village |
| East Nassau | 21 | 509 | 522 | -0.59% | 105 | 5 | Village |
| Valley Falls | 22 | 446 | 458 | -0.67% | 963 | 0 | Village |
Troy is the largest city in Rensselaer County, with a population of 50,787.
Valley Falls is the smallest city in Rensselaer County, with a population of 446.
There are 22 cities in Rensselaer County, New York.