19 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Thompson | 1 | 16,555 | 16,551 | -0.36% | 197 | 84.09 | Town |
| Fallsburg | 2 | 15,195 | 14,051 | 1.27% | 196 | 77.62 | Town |
| Mamakating | 3 | 12,550 | 12,645 | -0.44% | 131 | 96.11 | Town |
| Liberty | 4 | 10,385 | 10,161 | 0.04% | 130 | 79.58 | Town |
| Monticello | 5 | 7,210 | 7,237 | -0.07% | 1,767 | 4.08 | Village |
| Liberty | 6 | 5,201 | 5,023 | 0.7% | 1,984 | 2.62 | Village |
| Bethel | 7 | 4,367 | 3,952 | 3.09% | 51 | 85.27 | Town |
| Rockland | 8 | 3,328 | 3,285 | -0.03% | 35 | 94.16 | Town |
| Neversink | 9 | 3,322 | 3,369 | -0.69% | 40 | 82.77 | Town |
| Callicoon | 10 | 3,066 | 2,992 | 0.33% | 63 | 48.59 | Town |
| Lumberland | 11 | 2,326 | 2,243 | 0.82% | 50 | 46.54 | Town |
| Delaware | 12 | 2,176 | 2,198 | -0.5% | 62 | 34.90 | Town |
| Tusten | 13 | 1,431 | 1,405 | 0.07% | 30 | 47.20 | Town |
| Cochecton | 14 | 1,426 | 1,445 | -0.56% | 39 | 36.30 | Town |
| Fremont | 15 | 1,135 | 1,156 | -0.7% | 23 | 50.19 | Town |
| Wurtsboro | 16 | 1,071 | 1,085 | -0.28% | 857 | 1.25 | Village |
| Bloomingburg | 17 | 977 | 984 | -0.1% | 1,420 | 0.69 | Village |
| Woodridge | 18 | 711 | 710 | 0% | 425 | 1.67 | Village |
| Jeffersonville | 19 | 392 | 392 | 0% | 961 | 0.41 | Village |
Thompson is the largest city in Sullivan County, with a population of 16,555.
Jeffersonville is the smallest city in Sullivan County.
There are 19 cities in Sullivan County, New York.