16 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Seneca Falls town | 1 | 8,739 | 9,074 | -0.69% | 361 | 24.22 | Town |
| Seneca Falls | 2 | 8,619 | 6,276 | 7.15% | 1,839 | 4.69 | CDP |
| Waterloo town | 3 | 7,189 | 7,363 | -0.55% | 332 | 21.67 | Town |
| Waterloo | 4 | 4,607 | 4,849 | -1.03% | 2,136 | 2.16 | Village |
| Fayette town | 5 | 3,505 | 3,649 | -0.93% | 64 | 54.82 | Town |
| Ovid town | 6 | 2,744 | 2,845 | -0.76% | 89 | 30.86 | Town |
| Romulus town | 7 | 2,299 | 2,895 | -0.69% | 61 | 37.79 | Town |
| Covert town | 8 | 2,052 | 2,150 | -0.92% | 65 | 31.39 | Town |
| Varick town | 9 | 1,591 | 1,658 | -0.93% | 50 | 31.99 | Town |
| Lodi town | 10 | 1,442 | 1,483 | -0.89% | 42 | 34.19 | Town |
| Junius town | 11 | 1,342 | 1,388 | -0.81% | 50 | 26.71 | Town |
| Tyre town | 12 | 972 | 1,011 | -0.82% | 32 | 30.06 | Town |
| Interlaken | 13 | 604 | 631 | -0.82% | 1,967 | 0.31 | Village |
| Ovid | 14 | 519 | 551 | -1.14% | 1,304 | 0.40 | Village |
| Romulus | 15 | 376 | 431 | -0.79% | 617 | 0.61 | CDP |
| Lodi | 16 | 276 | 288 | -0.72% | 501 | 0.55 | Village |
Seneca Falls town is the largest city in Seneca County, with a population of 8,739.
Lodi is the smallest city in Seneca County.
There are 16 cities in Seneca County, New York.