13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Key West | 1 | 24,265 | 26,360 | -1.7% | 4,334 | 5.60 | City |
| Key Largo | 2 | 12,418 | 9,670 | 1.07% | 1,031 | 12.05 | CDP |
| Marathon | 3 | 9,845 | 9,855 | -0.02% | 1,166 | 8.45 | City |
| Islamorada, Village Islands | 4 | 6,898 | 7,122 | -0.65% | 1,070 | 6.45 | Village |
| Stock Island | 5 | 4,725 | 4,692 | 1.13% | 5,645 | 0.84 | CDP |
| Big Pine Key | 6 | 4,564 | 4,853 | 0.44% | 447 | 10.20 | CDP |
| Big Coppitt Key | 7 | 3,371 | 2,644 | 1.84% | 2,921 | 1.15 | CDP |
| Cudjoe Key | 8 | 2,357 | 2,157 | 1.73% | 456 | 5.17 | CDP |
| Tavernier | 9 | 2,292 | 1,980 | 0.44% | 912 | 2.51 | CDP |
| North Key Largo | 10 | 1,278 | 884 | 0.16% | 69 | 18.58 | CDP |
| Duck Key | 11 | 758 | 761 | 1.2% | 1,265 | 0.60 | CDP |
| Key Colony Beach | 12 | 735 | 787 | -1.34% | 1,670 | 0.44 | City |
| Layton | 13 | 196 | 211 | -1.51% | 1,210 | 0.16 | City |
Key West is the largest city in Monroe County, with a population of 24,265.
Layton is the smallest city in Monroe County.
There are 13 cities in Monroe County, Florida.