13 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sioux Center | 1 | 8,890 | 8,244 | 1.23% | 1,327 | 7 | City |
| Orange City | 2 | 6,681 | 6,279 | 1.01% | 1,450 | 5 | City |
| Rock Valley | 3 | 3,999 | 4,073 | -0.3% | 896 | 4 | City |
| Hawarden | 4 | 2,598 | 2,694 | -0.61% | 938 | 3 | City |
| Hull | 5 | 2,507 | 2,362 | 0.97% | 1,772 | 1 | City |
| Alton | 6 | 1,253 | 1,238 | 0.24% | 659 | 2 | City |
| Hospers | 7 | 694 | 720 | -0.57% | 1,314 | 1 | City |
| Boyden | 8 | 690 | 701 | -0.29% | 1,009 | 1 | City |
| Ireton | 9 | 565 | 582 | -0.53% | 554 | 1 | City |
| Granville | 10 | 297 | 311 | -0.67% | 1,021 | 0 | City |
| Maurice | 11 | 272 | 268 | 0.37% | 452 | 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 8,890.
Chatsworth is the smallest city in Sioux County, with a population of 72.
There are 13 cities in Sioux County, Iowa.