13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sioux Center | 1 | 8,739 | 8,249 | 1.13% | 1,385 | 6.31 | City |
| Orange City | 2 | 6,477 | 6,277 | 0.62% | 1,405 | 4.61 | City |
| Rock Valley | 3 | 4,030 | 4,067 | -0.17% | 903 | 4.46 | City |
| Hawarden | 4 | 2,608 | 2,697 | -0.69% | 942 | 2.77 | City |
| Hull | 5 | 2,468 | 2,378 | 0.73% | 1,744 | 1.42 | City |
| Alton | 6 | 1,242 | 1,244 | 0% | 653 | 1.90 | City |
| Hospers | 7 | 697 | 719 | -0.57% | 1,320 | 0.53 | City |
| Boyden | 8 | 694 | 701 | -0.14% | 1,015 | 0.68 | City |
| Ireton | 9 | 572 | 587 | -0.52% | 561 | 1.02 | City |
| Granville | 10 | 297 | 311 | -1% | 1,021 | 0.29 | City |
| Maurice | 11 | 274 | 268 | 0.37% | 455 | 0.60 | City |
| Matlock | 12 | 77 | 76 | 0% | 204 | 0.38 | City |
| Chatsworth | 13 | 74 | 74 | 0% | 149 | 0.50 | City |
Sioux Center is the largest city in Sioux County, with a population of 8,739.
Chatsworth is the smallest city in Sioux County.
There are 13 cities in Sioux County, Iowa.