26 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Grand River | 1 | 3,284 | 4,398 | 0.21% | 92 | 36 | Township |
| Grand River | 2 | 3,284 | 4,978 | 0.21% | 92 | 36 | Township |
| Maysville | 3 | 1,087 | 1,093 | -0.09% | 949 | 1 | City |
| Maysville | 4 | 1,087 | 1,090 | -0.09% | 949 | 1 | City |
| Stewartsville | 5 | 732 | 738 | -0.14% | 741 | 1 | City |
| Stewartsville | 6 | 732 | 736 | -0.14% | 741 | 1 | City |
| Colfax | 7 | 694 | 692 | -0.29% | 17 | 42 | Township |
| Colfax | 8 | 694 | 692 | -0.29% | 17 | 42 | Township |
| Adams | 9 | 630 | 639 | -0.63% | 15 | 42 | Township |
| Adams | 10 | 630 | 638 | -0.63% | 15 | 42 | Township |
| Sherman | 11 | 483 | 488 | -0.21% | 9 | 56 | Township |
| Sherman | 12 | 483 | 487 | -0.21% | 9 | 56 | Township |
| Union Star | 13 | 376 | 381 | -0.27% | 1,435 | 0 | Town |
| Union Star | 14 | 376 | 380 | -0.27% | 1,435 | 0 | Town |
| Osborn | 15 | 375 | 374 | 0% | 658 | 1 | City |
| Osborn | 16 | 375 | 373 | 0% | 658 | 1 | City |
| Grant | 17 | 341 | 341 | -0.29% | 7 | 50 | Township |
| Grant | 18 | 341 | 340 | -0.29% | 7 | 50 | Township |
| Dallas | 19 | 267 | 269 | -0.37% | 6 | 42 | Township |
| Dallas | 20 | 267 | 268 | -0.37% | 6 | 42 | Township |
| Clarksdale | 21 | 246 | 247 | 0% | 759 | 0 | City |
| Clarksdale | 22 | 246 | 246 | 0% | 759 | 0 | City |
| Weatherby | 23 | 78 | 78 | 0% | 661 | 0 | Town |
| Weatherby | 24 | 78 | 78 | 0% | 661 | 0 | Town |
| Amity | 25 | 26 | 26 | 0% | 150 | 0 | Town |
| Amity | 26 | 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 26 cities in DeKalb County, Missouri.