15 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ottawa | 1 | 4,393 | 4,450 | -0.25% | 966 | 4.55 | Village |
| Leipsic | 2 | 2,153 | 2,188 | -0.32% | 584 | 3.68 | Village |
| Columbus Grove | 3 | 2,118 | 2,150 | -0.28% | 1,725 | 1.23 | Village |
| Kalida | 4 | 1,448 | 1,452 | -0.07% | 861 | 1.68 | Village |
| Pandora | 5 | 1,182 | 1,197 | -0.25% | 1,109 | 1.07 | Village |
| Continental | 6 | 1,078 | 1,100 | -0.37% | 901 | 1.20 | Village |
| Glandorf | 7 | 980 | 965 | 0.31% | 564 | 1.74 | Village |
| Ottoville | 8 | 971 | 968 | 0.1% | 1,025 | 0.95 | Village |
| Fort Jennings | 9 | 527 | 522 | 0.19% | 936 | 0.56 | Village |
| Dupont | 10 | 204 | 208 | -0.49% | 223 | 0.91 | Village |
| Cloverdale | 11 | 165 | 169 | -0.6% | 268 | 0.62 | Village |
| Gilboa | 12 | 164 | 168 | -0.61% | 1,252 | 0.13 | Village |
| Vaughnsville | 13 | 133 | 271 | -6.34% | 778 | 0.17 | CDP |
| Miller City | 14 | 126 | 133 | -0.79% | 318 | 0.40 | Village |
| Belmore | 15 | 59 | 61 | 0% | 133 | 0.44 | Village |
Ottawa is the largest city in Putnam County, with a population of 4,393.
Belmore is the smallest city in Putnam County.
There are 15 cities in Putnam County, Ohio.