| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Indianola | 1 | 17,062 | 15,882 | 1.38% | 1,492 | 11 | City |
| Norwalk | 2 | 15,371 | 12,861 | 2.45% | 1,320 | 12 | City |
| Carlisle | 3 | 4,611 | 4,185 | 1.74% | 772 | 6 | City |
| Milo | 4 | 786 | 777 | 0.26% | 1,293 | 1 | City |
| Hartford | 5 | 750 | 733 | 0.4% | 689 | 1 | City |
| Cumming | 6 | 586 | 436 | 4.64% | 170 | 3 | City |
| New Virginia | 7 | 509 | 500 | 0.39% | 1,131 | 0 | City |
| Martensdale | 8 | 426 | 428 | 0% | 1,121 | 0 | City |
| Lacona | 9 | 344 | 345 | 0% | 1,039 | 0 | City |
| St. Marys | 10 | 125 | 118 | 0.81% | 887 | 0 | City |
| Ackworth | 11 | 122 | 117 | 0.83% | 222 | 1 | City |
| Spring Hill | 12 | 72 | 66 | 1.41% | 576 | 0 | City |
| Sandyville | 13 | 61 | 58 | 0% | 123 | 0 | City |
Indianola is the largest city in Warren County, with a population of 17,062.
Sandyville is the smallest city in Warren County, with a population of 61.
There are 13 cities in Warren County, Iowa.