22 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Carmel | 1 | 34,127 | 33,581 | 0.4% | 951 | 36 | Town |
| Carmel | 2 | 34,127 | 33,604 | 0.4% | 951 | 36 | Town |
| Southeast | 3 | 18,490 | 18,074 | 0.82% | 583 | 32 | Town |
| Southeast | 4 | 18,490 | 18,044 | 0.82% | 583 | 32 | Town |
| Putnam Valley | 5 | 11,776 | 11,751 | 0.27% | 286 | 41 | Town |
| Putnam Valley | 6 | 11,776 | 11,738 | 0.27% | 286 | 41 | Town |
| Patterson | 7 | 11,638 | 11,535 | 0.41% | 361 | 32 | Town |
| Patterson | 8 | 11,638 | 11,523 | 0.41% | 361 | 32 | Town |
| Philipstown | 9 | 9,915 | 9,828 | 0.34% | 203 | 49 | Town |
| Philipstown | 10 | 9,915 | 9,819 | 0.34% | 203 | 49 | Town |
| Carmel | 11 | 9,075 | 6,841 | 7.14% | 983 | 9 | CDP |
| Mahopac | 12 | 8,875 | 8,914 | 0.37% | 1,448 | 6 | CDP |
| Putnam Lake | 13 | 3,822 | 3,943 | -0.03% | 839 | 5 | CDP |
| Brewster Hill | 14 | 2,688 | 2,574 | 1.51% | 3,090 | 1 | CDP |
| Brewster | 15 | 2,503 | 2,510 | -0.04% | 5,098 | 0 | Village |
| Brewster | 16 | 2,503 | 2,507 | -0.04% | 5,098 | 0 | Village |
| Cold Spring | 17 | 1,997 | 1,986 | 0.1% | 3,362 | 1 | Village |
| Cold Spring | 18 | 1,997 | 1,984 | 0.1% | 3,362 | 1 | Village |
| Brewster Heights | 19 | 1,578 | 1,067 | 7.2% | 2,994 | 1 | CDP |
| Peach Lake | 20 | 1,279 | 1,932 | -1.77% | 555 | 2 | CDP |
| Nelsonville | 21 | 633 | 624 | 0.32% | 612 | 1 | Village |
| Nelsonville | 22 | 633 | 623 | 0.32% | 612 | 1 | Village |
Carmel is the largest city in Putnam County, with a population of 34,127.
Nelsonville is the smallest city in Putnam County, with a population of 633.
There are 22 cities in Putnam County, New York.