13 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Black | 1 | 8,825 | 8,982 | -0.14% | 102 | 87 | Township |
| Mount Vernon | 2 | 6,270 | 6,482 | -0.56% | 2,179 | 3 | City |
| Marrs | 3 | 5,407 | 5,390 | 0.17% | 105 | 51 | Township |
| Robinson | 4 | 3,904 | 3,883 | 0.21% | 100 | 39 | Township |
| Robb | 5 | 1,770 | 1,739 | 0.4% | 47 | 37 | Township |
| Center | 6 | 1,464 | 1,468 | 0.07% | 58 | 25 | Township |
| Smith | 7 | 1,101 | 1,096 | 0.18% | 52 | 21 | Township |
| Poseyville | 8 | 969 | 965 | 0.1% | 1,502 | 1 | Town |
| New Harmony | 9 | 681 | 695 | -0.29% | 836 | 1 | Town |
| Cynthiana | 10 | 554 | 554 | 0% | 1,388 | 0 | Town |
| Point | 11 | 333 | 324 | 0.6% | 7 | 51 | Township |
| Bethel | 12 | 256 | 253 | 0.39% | 13 | 19 | Township |
| Griffin | 13 | 141 | 143 | 0% | 2,074 | 0 | Town |
Black is the largest city in Posey County, with a population of 8,825.
Griffin is the smallest city in Posey County, with a population of 141.
There are 13 cities in Posey County, Indiana.