15 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Kirksville | 1 | 17,921 | 17,545 | 0.45% | 1,246 | 14 | City |
| Kirksville | 2 | 17,921 | 17,519 | 0.45% | 1,246 | 14 | City |
| Greentop | 3 | 391 | 387 | 0.26% | 479 | 1 | City |
| Greentop | 4 | 391 | 385 | 0.26% | 479 | 1 | City |
| Novinger | 5 | 384 | 384 | 0% | 488 | 1 | City |
| Novinger | 6 | 384 | 383 | 0% | 488 | 1 | City |
| Brashear | 7 | 241 | 241 | 0% | 689 | 0 | City |
| Brashear | 8 | 241 | 240 | 0% | 689 | 0 | City |
| Connelsville | 9 | 110 | 111 | 6.8% | 332 | 0 | CDP |
| Millard | 10 | 81 | 78 | 0% | 675 | 0 | Village |
| Millard | 11 | 81 | 78 | 0% | 675 | 0 | Village |
| Gibbs | 12 | 76 | 76 | 0% | 306 | 0 | Village |
| Gibbs | 13 | 76 | 76 | 0% | 306 | 0 | Village |
| South Gifford | 14 | 21 | 21 | 0% | 102 | 0 | Village |
| South Gifford | 15 | 21 | 21 | 0% | 102 | 0 | Village |
Kirksville is the largest city in Adair County, with a population of 17,921.
South Gifford is the smallest city in Adair County, with a population of 21.
There are 15 cities in Adair County, Missouri.