21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Amsterdam | 1 | 18,161 | 18,198 | -0.04% | 3,092 | 6 | City |
| Amsterdam | 2 | 5,615 | 5,564 | 0% | 189 | 30 | Town |
| Minden | 3 | 4,212 | 4,163 | 0.29% | 83 | 51 | Town |
| Canajoharie | 4 | 3,644 | 3,655 | 0.03% | 86 | 43 | Town |
| Palatine | 5 | 3,255 | 3,188 | 0.9% | 79 | 41 | Town |
| Glen | 6 | 2,604 | 2,535 | 0.23% | 67 | 39 | Town |
| St. Johnsville | 7 | 2,596 | 2,588 | 0.23% | 154 | 17 | Town |
| Canajoharie | 8 | 2,060 | 2,080 | -0.19% | 1,548 | 1 | Village |
| Fort Plain | 9 | 1,999 | 2,013 | -0.15% | 1,486 | 1 | Village |
| Root | 10 | 1,989 | 2,014 | -0.15% | 39 | 51 | Town |
| Esperance | 11 | 1,813 | 1,805 | 0.28% | 92 | 20 | Town |
| St. Johnsville | 12 | 1,708 | 1,722 | -0.18% | 1,945 | 1 | Village |
| Charleston | 13 | 1,346 | 1,357 | 0% | 32 | 42 | Town |
| Hagaman | 14 | 1,115 | 1,127 | -0.27% | 744 | 1 | Village |
| Fultonville | 15 | 792 | 747 | 1.15% | 1,660 | 0 | Village |
| Palatine Bridge | 16 | 786 | 793 | -0.25% | 853 | 1 | Village |
| Fonda | 17 | 690 | 695 | -0.14% | 1,280 | 1 | Village |
| Nelliston | 18 | 572 | 569 | 0% | 518 | 1 | Village |
| Fort Johnson | 19 | 431 | 425 | 0.23% | 583 | 1 | Village |
| Esperance | 20 | 351 | 354 | -0.28% | 718 | 0 | Village |
| Ames | 21 | 139 | 141 | -0.71% | 1,061 | 0 | Village |
Amsterdam is the largest city in Montgomery County, with a population of 18,161.
Ames is the smallest city in Montgomery County, with a population of 139.
There are 21 cities in Montgomery County, New York.