13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Grand River | 1 | 3,284 | 4,978 | 0.21% | 92 | 36 | Township |
| Maysville | 2 | 1,087 | 1,090 | -0.09% | 949 | 1 | City |
| Stewartsville | 3 | 732 | 736 | -0.14% | 741 | 1 | City |
| Colfax | 4 | 694 | 692 | -0.29% | 17 | 42 | Township |
| Adams | 5 | 630 | 638 | -0.63% | 15 | 42 | Township |
| Sherman | 6 | 483 | 487 | -0.21% | 9 | 56 | Township |
| Union Star | 7 | 376 | 380 | -0.27% | 1,435 | 0 | Town |
| Osborn | 8 | 375 | 373 | 0% | 658 | 1 | City |
| Grant | 9 | 341 | 340 | -0.29% | 7 | 50 | Township |
| Dallas | 10 | 267 | 268 | -0.37% | 6 | 42 | Township |
| Clarksdale | 11 | 246 | 246 | 0% | 759 | 0 | City |
| Weatherby | 12 | 78 | 78 | 0% | 661 | 0 | Town |
| Amity | 13 | 26 | 26 | 0% | 150 | 0 | Town |
Grand River is the largest city in DeKalb County, with a population of 3,284.
Amity is the smallest city in DeKalb County, with a population of 26.
There are 13 cities in DeKalb County, Missouri.