21 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Amsterdam | 1 | 18,154 | 18,198 | -0.04% | 3,091 | 6 | City |
| Amsterdam | 2 | 5,615 | 5,564 | 0% | 189 | 30 | Town |
| Minden | 3 | 4,224 | 4,163 | 0.28% | 83 | 51 | Town |
| Canajoharie | 4 | 3,645 | 3,655 | 0.03% | 86 | 43 | Town |
| Palatine | 5 | 3,284 | 3,188 | 0.89% | 80 | 41 | Town |
| Glen | 6 | 2,610 | 2,535 | 0.23% | 68 | 39 | Town |
| St. Johnsville | 7 | 2,602 | 2,588 | 0.23% | 154 | 17 | Town |
| Canajoharie | 8 | 2,056 | 2,080 | -0.19% | 1,545 | 1 | Village |
| Fort Plain | 9 | 1,996 | 2,013 | -0.15% | 1,484 | 1 | Village |
| Root | 10 | 1,986 | 2,014 | -0.15% | 39 | 51 | Town |
| Esperance | 11 | 1,818 | 1,805 | 0.28% | 92 | 20 | Town |
| St. Johnsville | 12 | 1,705 | 1,722 | -0.18% | 1,942 | 1 | Village |
| Charleston | 13 | 1,346 | 1,357 | 0% | 32 | 42 | Town |
| Hagaman | 14 | 1,113 | 1,127 | -0.18% | 743 | 1 | Village |
| Fultonville | 15 | 801 | 747 | 1.14% | 1,679 | 0 | Village |
| Palatine Bridge | 16 | 785 | 793 | -0.13% | 852 | 1 | Village |
| Fonda | 17 | 689 | 695 | -0.14% | 1,278 | 1 | Village |
| Nelliston | 18 | 573 | 569 | 0.17% | 519 | 1 | Village |
| Fort Johnson | 19 | 432 | 425 | 0.23% | 585 | 1 | Village |
| Esperance | 20 | 351 | 354 | 0% | 718 | 0 | Village |
| Ames | 21 | 139 | 141 | 0% | 1,061 | 0 | Village |
Amsterdam is the largest city in Montgomery County, with a population of 18,154.
Ames is the smallest city in Montgomery County, with a population of 139.
There are 21 cities in Montgomery County, New York.