| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Amsterdam | 1 | 18,072 | 18,191 | -0.12% | 3,077 | 6 | City |
| Amsterdam | 2 | 6,303 | 5,565 | 5.86% | 213 | 30 | Town |
| Minden | 3 | 4,249 | 4,172 | 0.54% | 83 | 51 | Town |
| Canajoharie | 4 | 3,652 | 3,664 | 0.08% | 86 | 43 | Town |
| Palatine | 5 | 3,232 | 3,182 | 0.15% | 79 | 41 | Town |
| Glen | 6 | 2,701 | 2,532 | 1.96% | 70 | 39 | Town |
| St. Johnsville | 7 | 2,591 | 2,590 | 0.08% | 154 | 17 | Town |
| Canajoharie | 8 | 2,053 | 2,083 | -0.29% | 1,542 | 1 | Village |
| Root | 9 | 2,006 | 2,015 | 0.2% | 40 | 51 | Town |
| Fort Plain | 10 | 2,001 | 2,015 | -0.2% | 1,488 | 1 | Village |
| Esperance | 11 | 1,803 | 1,804 | -0.11% | 92 | 20 | Town |
| St. Johnsville | 12 | 1,701 | 1,723 | -0.29% | 1,937 | 1 | Village |
| Charleston | 13 | 1,363 | 1,356 | 0.52% | 32 | 42 | Town |
| Hagaman | 14 | 1,115 | 1,132 | -0.36% | 744 | 1 | Village |
| Fultonville | 15 | 798 | 746 | 1.01% | 1,673 | 0 | Village |
| Palatine Bridge | 16 | 790 | 793 | -0.25% | 858 | 1 | Village |
| Fonda | 17 | 686 | 695 | -0.29% | 1,273 | 1 | Village |
| Nelliston | 18 | 564 | 564 | 0% | 510 | 1 | Village |
| Esperance | 19 | 345 | 354 | -0.58% | 706 | 0 | Village |
| Ames | 20 | 137 | 142 | -0.72% | 1,046 | 0 | Village |
Amsterdam is the largest city in Montgomery County, with a population of 18,072.
Ames is the smallest city in Montgomery County, with a population of 137.
There are 20 cities in Montgomery County, New York.