27 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Black | 1 | 8,837 | 9,001 | -0.14% | 102 | 87 | Township |
| Black | 2 | 8,837 | 8,982 | -0.14% | 102 | 87 | Township |
| Mount Vernon | 3 | 6,305 | 6,498 | -0.57% | 2,191 | 3 | City |
| Mount Vernon | 4 | 6,305 | 6,482 | -0.57% | 2,191 | 3 | City |
| Marrs | 5 | 5,398 | 5,394 | 0.17% | 105 | 51 | Township |
| Marrs | 6 | 5,398 | 5,390 | 0.17% | 105 | 51 | Township |
| Robinson | 7 | 3,896 | 3,887 | 0.21% | 100 | 39 | Township |
| Robinson | 8 | 3,896 | 3,883 | 0.21% | 100 | 39 | Township |
| Robb | 9 | 1,763 | 1,740 | 0.4% | 47 | 37 | Township |
| Robb | 10 | 1,763 | 1,739 | 0.4% | 47 | 37 | Township |
| Center | 11 | 1,463 | 1,469 | 0.07% | 58 | 25 | Township |
| Center | 12 | 1,463 | 1,468 | 0.07% | 58 | 25 | Township |
| Smith | 13 | 1,099 | 1,096 | 0.18% | 52 | 21 | Township |
| Smith | 14 | 1,099 | 1,096 | 0.18% | 52 | 21 | Township |
| Poseyville | 15 | 968 | 967 | 0% | 1,501 | 1 | Town |
| Poseyville | 16 | 968 | 965 | 0% | 1,501 | 1 | Town |
| New Harmony | 17 | 683 | 696 | -0.44% | 838 | 1 | Town |
| New Harmony | 18 | 683 | 695 | -0.44% | 838 | 1 | Town |
| Cynthiana | 19 | 554 | 553 | 0% | 1,388 | 0 | Town |
| Cynthiana | 20 | 554 | 554 | 0% | 1,388 | 0 | Town |
| Parkers Settlement | 21 | 506 | 591 | -2.69% | 289 | 2 | CDP |
| Point | 22 | 331 | 325 | 0.61% | 7 | 51 | Township |
| Point | 23 | 331 | 324 | 0.61% | 7 | 51 | Township |
| Bethel | 24 | 255 | 253 | 0.39% | 13 | 19 | Township |
| Bethel | 25 | 255 | 253 | 0.39% | 13 | 19 | Township |
| Griffin | 26 | 141 | 143 | -0.7% | 2,074 | 0 | Town |
| Griffin | 27 | 141 | 143 | -0.7% | 2,074 | 0 | Town |
Black is the largest city in Posey County, with a population of 8,837.
Griffin is the smallest city in Posey County, with a population of 141.
There are 27 cities in Posey County, Indiana.