15 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sullivan | 1 | 4,235 | 4,259 | -0.12% | 2,259 | 2 | City |
| Haddon | 2 | 3,728 | 3,750 | -0.24% | 52 | 71 | Township |
| Curry | 3 | 3,405 | 3,411 | -0.32% | 97 | 35 | Township |
| Cass | 4 | 1,842 | 1,848 | -0.38% | 49 | 38 | Township |
| Jackson | 5 | 1,730 | 1,728 | -0.23% | 40 | 43 | Township |
| Shelburn | 6 | 1,112 | 1,104 | 0.09% | 1,609 | 1 | Town |
| Turman | 7 | 1,073 | 1,079 | -0.37% | 19 | 57 | Township |
| Farmersburg | 8 | 1,065 | 1,068 | -0.09% | 1,433 | 1 | Town |
| Dugger | 9 | 794 | 796 | -0.13% | 1,355 | 1 | Town |
| Gill | 10 | 790 | 793 | -0.25% | 13 | 60 | Township |
| Fairbanks | 11 | 711 | 711 | -0.42% | 17 | 41 | Township |
| Hymera | 12 | 662 | 656 | 0.15% | 930 | 1 | Town |
| Carlisle | 13 | 613 | 620 | -0.33% | 1,183 | 1 | Town |
| Jefferson | 14 | 362 | 365 | -0.55% | 9 | 42 | Township |
| Merom | 15 | 209 | 209 | 0% | 589 | 0 | Town |
Sullivan is the largest city in Sullivan County, with a population of 4,235.
Merom is the smallest city in Sullivan County, with a population of 209.
There are 15 cities in Sullivan County, Indiana.