13 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Norwalk | 1 | 16,635 | 12,917 | 3.87% | 1,428 | 12 | City |
| Indianola | 2 | 16,514 | 15,863 | 0.66% | 1,444 | 11 | City |
| Carlisle | 3 | 4,487 | 4,169 | 1.2% | 751 | 6 | City |
| Milo | 4 | 755 | 775 | -0.4% | 1,242 | 1 | City |
| Hartford | 5 | 726 | 734 | -0.14% | 667 | 1 | City |
| Cumming | 6 | 573 | 434 | 4.18% | 166 | 3 | City |
| New Virginia | 7 | 497 | 503 | -0.2% | 1,104 | 0 | City |
| Martensdale | 8 | 408 | 422 | -0.49% | 1,074 | 0 | City |
| Lacona | 9 | 332 | 344 | -0.6% | 1,003 | 0 | City |
| Ackworth | 10 | 117 | 116 | 0% | 213 | 1 | City |
| St. Marys | 11 | 116 | 115 | 0% | 823 | 0 | City |
| Spring Hill | 12 | 69 | 65 | 1.47% | 552 | 0 | City |
| Sandyville | 13 | 60 | 57 | 1.69% | 121 | 0 | City |
Norwalk is the largest city in Warren County, with a population of 16,635.
Sandyville is the smallest city in Warren County, with a population of 60.
There are 13 cities in Warren County, Iowa.