| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ottawa | 1 | 4,427 | 4,453 | -0.23% | 974 | 5 | Village |
| Leipsic | 2 | 2,160 | 2,183 | -0.32% | 586 | 4 | Village |
| Columbus Grove | 3 | 2,125 | 2,149 | -0.33% | 1,730 | 1 | Village |
| Kalida | 4 | 1,479 | 1,461 | -0.14% | 880 | 2 | Village |
| Pandora | 5 | 1,135 | 1,198 | -1.22% | 1,065 | 1 | Village |
| Continental | 6 | 1,100 | 1,105 | -0.27% | 919 | 1 | Village |
| Glandorf | 7 | 988 | 965 | 0.3% | 569 | 2 | Village |
| Ottoville | 8 | 976 | 959 | 0.1% | 1,031 | 1 | Village |
| Fort Jennings | 9 | 533 | 523 | 0.19% | 947 | 1 | Village |
| Dupont | 10 | 207 | 209 | -0.48% | 227 | 1 | Village |
| Cloverdale | 11 | 169 | 172 | -0.59% | 274 | 1 | Village |
| Gilboa | 12 | 167 | 172 | -0.6% | 1,275 | 0 | Village |
| Miller City | 13 | 131 | 133 | -0.76% | 331 | 0 | Village |
| Belmore | 14 | 62 | 64 | -1.59% | 140 | 0 | Village |
Ottawa is the largest city in Putnam County, with a population of 4,427.
Belmore is the smallest city in Putnam County, with a population of 62.
There are 14 cities in Putnam County, Ohio.