25 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ottawa | 1 | 7,999 | 8,029 | -0.05% | 222 | 36 | Township |
| Ottawa | 2 | 4,402 | 4,462 | -0.23% | 968 | 5 | Village |
| Pleasant | 3 | 3,729 | 3,783 | -0.08% | 103 | 36 | Township |
| Union | 4 | 2,952 | 2,945 | 0.1% | 97 | 30 | Township |
| Riley | 5 | 2,174 | 2,231 | -0.5% | 72 | 30 | Township |
| Leipsic | 6 | 2,145 | 2,186 | -0.33% | 582 | 4 | Village |
| Columbus Grove | 7 | 2,110 | 2,151 | -0.33% | 1,718 | 1 | Village |
| Monterey | 8 | 2,040 | 2,041 | -0.05% | 83 | 25 | Township |
| Jennings | 9 | 2,004 | 2,020 | -0.25% | 71 | 28 | Township |
| Liberty | 10 | 1,657 | 1,673 | -0.24% | 46 | 36 | Township |
| Kalida | 11 | 1,448 | 1,456 | -0.07% | 861 | 2 | Village |
| Greensburg | 12 | 1,427 | 1,424 | -0.14% | 47 | 30 | Township |
| Blanchard | 13 | 1,193 | 1,226 | -0.42% | 33 | 36 | Township |
| Palmer | 14 | 1,188 | 1,155 | 0.59% | 33 | 36 | Township |
| Pandora | 15 | 1,180 | 1,198 | -0.25% | 1,107 | 1 | Village |
| Sugar Creek | 16 | 1,139 | 1,178 | -0.61% | 37 | 30 | Township |
| Continental | 17 | 1,078 | 1,099 | -0.28% | 901 | 1 | Village |
| Glandorf | 18 | 987 | 966 | 0.41% | 568 | 2 | Village |
| Ottoville | 19 | 968 | 965 | 0.1% | 1,022 | 1 | Village |
| Fort Jennings | 20 | 533 | 523 | 0.38% | 947 | 1 | Village |
| Dupont | 21 | 204 | 209 | -0.49% | 223 | 1 | Village |
| Cloverdale | 22 | 168 | 171 | 0% | 273 | 1 | Village |
| Gilboa | 23 | 160 | 168 | -0.62% | 1,221 | 0 | Village |
| Miller City | 24 | 130 | 133 | 0% | 328 | 0 | Village |
| Belmore | 25 | 58 | 60 | 0% | 131 | 0 | Village |
Ottawa is the largest city in Putnam County, with a population of 7,999.
Belmore is the smallest city in Putnam County, with a population of 58.
There are 25 cities in Putnam County, Ohio.