15 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sullivan | 1 | 4,199 | 4,258 | -0.28% | 2,239 | 1.88 | City |
| Haddon township | 2 | 3,759 | 3,748 | 0.27% | 53 | 71.23 | Township |
| Curry township | 3 | 3,483 | 3,413 | 0.9% | 100 | 34.96 | Township |
| Cass township | 4 | 1,881 | 1,849 | 0.86% | 50 | 37.82 | Township |
| Jackson township | 5 | 1,776 | 1,728 | 1.08% | 41 | 43.26 | Township |
| Shelburn | 6 | 1,125 | 1,105 | 0.36% | 1,628 | 0.69 | Town |
| Turman township | 7 | 1,099 | 1,079 | 0.83% | 19 | 56.80 | Township |
| Farmersburg | 8 | 1,063 | 1,068 | -0.09% | 1,431 | 0.74 | Town |
| Gill township | 9 | 802 | 791 | 0.75% | 13 | 60.12 | Township |
| Dugger | 10 | 795 | 797 | 0% | 1,357 | 0.59 | Town |
| Fairbanks township | 11 | 720 | 711 | 0.7% | 18 | 40.99 | Township |
| Hymera | 12 | 661 | 655 | 0.15% | 928 | 0.71 | Town |
| Carlisle | 13 | 612 | 621 | -0.33% | 1,181 | 0.52 | Town |
| Jefferson township | 14 | 369 | 363 | 0.82% | 9 | 42.39 | Township |
| Merom | 15 | 208 | 208 | 0% | 586 | 0.35 | Town |
Sullivan is the largest city in Sullivan County, with a population of 4,199.
Merom is the smallest city in Sullivan County.
There are 15 cities in Sullivan County, Indiana.