| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Seneca Falls | 1 | 8,817 | 8,996 | -0.32% | 364 | 24 | Town |
| Waterloo | 2 | 7,175 | 7,371 | -0.53% | 331 | 22 | Town |
| Waterloo | 3 | 4,634 | 4,859 | -0.86% | 2,148 | 2 | Village |
| Romulus | 4 | 3,655 | 3,415 | 8.84% | 97 | 38 | Town |
| Fayette | 5 | 3,578 | 3,663 | -0.14% | 65 | 55 | Town |
| Ovid | 6 | 2,257 | 2,313 | -0.31% | 73 | 31 | Town |
| Covert | 7 | 2,100 | 2,149 | -0.1% | 67 | 31 | Town |
| Varick | 8 | 1,639 | 1,658 | 0.24% | 51 | 32 | Town |
| Lodi | 9 | 1,477 | 1,487 | -0.07% | 43 | 34 | Town |
| Junius | 10 | 1,361 | 1,387 | -0.22% | 51 | 27 | Town |
| Tyre | 11 | 973 | 1,006 | -0.51% | 32 | 30 | Town |
| Interlaken | 12 | 602 | 625 | -0.66% | 1,961 | 0 | Village |
| Ovid | 13 | 507 | 545 | -1.36% | 1,274 | 0 | Village |
| Lodi | 14 | 271 | 286 | -1.09% | 492 | 1 | Village |
Seneca Falls is the largest city in Seneca County, with a population of 8,817.
Lodi is the smallest city in Seneca County, with a population of 271.
There are 14 cities in Seneca County, New York.