20 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Thompson | 1 | 16,760 | 16,555 | 0.07% | 199 | 84 | Town |
| Fallsburg | 2 | 15,359 | 14,049 | 1.12% | 198 | 78 | Town |
| Mamakating | 3 | 12,729 | 12,650 | 0.03% | 132 | 96 | Town |
| Liberty | 4 | 10,289 | 10,170 | -0.46% | 129 | 80 | Town |
| Monticello | 5 | 7,222 | 7,240 | -0.04% | 1,770 | 4 | Village |
| Liberty | 6 | 5,190 | 5,028 | 0.52% | 1,980 | 3 | Village |
| Bethel | 7 | 4,386 | 3,957 | 2.05% | 51 | 85 | Town |
| Neversink | 8 | 3,392 | 3,370 | 0.15% | 41 | 83 | Town |
| Rockland | 9 | 3,370 | 3,279 | 0.36% | 36 | 94 | Town |
| Callicoon | 10 | 3,054 | 2,988 | 0.03% | 63 | 49 | Town |
| Lumberland | 11 | 2,321 | 2,242 | 0.35% | 50 | 47 | Town |
| Delaware | 12 | 2,215 | 2,197 | 0.14% | 63 | 35 | Town |
| Tusten | 13 | 1,466 | 1,407 | 0.69% | 31 | 47 | Town |
| Cochecton | 14 | 1,432 | 1,446 | -0.35% | 39 | 36 | Town |
| Fremont | 15 | 1,142 | 1,156 | -0.35% | 23 | 50 | Town |
| Wurtsboro | 16 | 1,084 | 1,090 | -0.09% | 868 | 1 | Village |
| Bloomingburg | 17 | 974 | 985 | -0.2% | 1,416 | 1 | Village |
| Forestburgh | 18 | 827 | 807 | 0.36% | 15 | 55 | Town |
| Woodridge | 19 | 709 | 709 | 0% | 424 | 2 | Village |
| Jeffersonville | 20 | 391 | 391 | 0% | 958 | 0 | Village |
Thompson is the largest city in Sullivan County, with a population of 16,760.
Jeffersonville is the smallest city in Sullivan County, with a population of 391.
There are 20 cities in Sullivan County, New York.