13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Norwalk | 1 | 16,175 | 12,919 | 4.19% | 1,389 | 11.65 | City |
| Indianola | 2 | 16,164 | 15,861 | 0.38% | 1,414 | 11.44 | City |
| Carlisle | 3 | 4,432 | 4,166 | 1.21% | 784 | 5.65 | City |
| Milo | 4 | 750 | 777 | -0.66% | 1,234 | 0.61 | City |
| Hartford | 5 | 719 | 733 | -0.42% | 661 | 1.09 | City |
| Cumming | 6 | 547 | 432 | 4.39% | 159 | 3.45 | City |
| New Virginia | 7 | 489 | 499 | -0.41% | 1,087 | 0.45 | City |
| Martensdale | 8 | 403 | 422 | -0.98% | 1,061 | 0.38 | City |
| Lacona | 9 | 328 | 343 | -0.91% | 991 | 0.33 | City |
| Ackworth | 10 | 117 | 117 | 0% | 213 | 0.55 | City |
| St. Marys | 11 | 112 | 117 | -0.88% | 794 | 0.14 | City |
| Spring Hill | 12 | 68 | 67 | 0% | 544 | 0.13 | City |
| Sandyville | 13 | 59 | 58 | 0% | 119 | 0.49 | City |
Norwalk is the largest city in Warren County, with a population of 16,175.
Sandyville is the smallest city in Warren County.
There are 13 cities in Warren County, Iowa.