13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sioux Center | 1 | 8,782 | 8,244 | 1.23% | 1,392 | 6 | City |
| Orange City | 2 | 6,614 | 6,279 | 1.02% | 1,435 | 5 | City |
| Rock Valley | 3 | 4,011 | 4,073 | -0.32% | 899 | 4 | City |
| Hawarden | 4 | 2,614 | 2,694 | -0.61% | 944 | 3 | City |
| Hull | 5 | 2,483 | 2,362 | 0.98% | 1,755 | 1 | City |
| Alton | 6 | 1,250 | 1,238 | 0.16% | 657 | 2 | City |
| Hospers | 7 | 698 | 720 | -0.71% | 1,322 | 1 | City |
| Boyden | 8 | 692 | 701 | -0.29% | 1,012 | 1 | City |
| Ireton | 9 | 568 | 582 | -0.53% | 557 | 1 | City |
| Granville | 10 | 299 | 311 | -0.99% | 1,027 | 0 | City |
| Maurice | 11 | 271 | 268 | 0% | 450 | 1 | City |
| Matlock | 12 | 74 | 74 | 0% | 196 | 0 | City |
| Chatsworth | 13 | 72 | 72 | 0% | 145 | 0 | City |
Sioux Center is the largest city in Sioux County, with a population of 8,782.
Chatsworth is the smallest city in Sioux County, with a population of 72.
There are 13 cities in Sioux County, Iowa.