18 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Brazil | 1 | 8,674 | 8,567 | 0.43% | 1,341 | 6 | Township |
| Brazil | 2 | 8,259 | 8,158 | 0.24% | 2,240 | 4 | City |
| Posey | 3 | 4,028 | 4,052 | -0.2% | 115 | 35 | Township |
| Jackson | 4 | 2,808 | 2,834 | -0.18% | 80 | 35 | Township |
| Harrison | 5 | 2,164 | 2,163 | -0.05% | 35 | 62 | Township |
| Dick Johnson | 6 | 1,326 | 1,328 | -0.23% | 62 | 21 | Township |
| Harmony | 7 | 1,225 | 1,229 | 0.08% | 35 | 35 | Township |
| Perry | 8 | 910 | 915 | -0.11% | 20 | 45 | Township |
| Sugar Ridge | 9 | 906 | 921 | -0.44% | 33 | 28 | Township |
| Clay City | 10 | 886 | 876 | 0.23% | 1,644 | 1 | Town |
| Knightsville | 11 | 692 | 699 | -0.29% | 667 | 1 | Town |
| Harmony | 12 | 671 | 678 | -0.3% | 816 | 1 | Town |
| Harmony | 13 | 501 | 515 | -0.99% | 24 | 21 | Township |
| Staunton | 14 | 467 | 470 | -0.21% | 1,428 | 0 | Town |
| Cass | 15 | 339 | 342 | -0.29% | 28 | 12 | Township |
| Carbon | 16 | 257 | 260 | -0.39% | 1,725 | 0 | Town |
| Coalmont | 17 | 242 | 221 | -4.35% | 161 | 2 | CDP |
| Center Point | 18 | 210 | 214 | -0.47% | 284 | 1 | Town |
Brazil is the largest city in Clay County, with a population of 8,674.
Center Point is the smallest city in Clay County, with a population of 210.
There are 18 cities in Clay County, Indiana.