14 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Black township | 1 | 8,784 | 8,982 | -0.42% | 101 | 86.69 | Township |
| Mount Vernon | 2 | 6,273 | 6,477 | -0.65% | 2,180 | 2.88 | City |
| Marrs township | 3 | 5,369 | 5,390 | -0.13% | 104 | 51.47 | Township |
| Robinson township | 4 | 3,873 | 3,884 | -0.1% | 99 | 39.08 | Township |
| Robb township | 5 | 1,752 | 1,740 | 0.11% | 47 | 37.28 | Township |
| Center township | 6 | 1,455 | 1,468 | -0.27% | 58 | 25.17 | Township |
| Smith township | 7 | 1,086 | 1,095 | -0.18% | 51 | 21.23 | Township |
| Poseyville | 8 | 966 | 968 | 0% | 1,498 | 0.65 | Town |
| New Harmony | 9 | 680 | 694 | -0.44% | 834 | 0.81 | Town |
| Cynthiana | 10 | 547 | 551 | -0.18% | 1,371 | 0.40 | Town |
| Parkers Settlement | 11 | 506 | 591 | -2.69% | 289 | 1.75 | CDP |
| Point township | 12 | 328 | 325 | 0% | 6 | 50.54 | Township |
| Bethel township | 13 | 252 | 252 | 0% | 13 | 19.06 | Township |
| Griffin | 14 | 142 | 142 | 0% | 2,088 | 0.07 | Town |
Black township is the largest city in Posey County, with a population of 8,784.
Griffin is the smallest city in Posey County.
There are 14 cities in Posey County, Indiana.