52 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Oberlin | 1 | 1,605 | 1,632 | -0.31% | 840 | 2 | City |
| Oberlin | 2 | 1,605 | 1,628 | -0.31% | 840 | 2 | City |
| Dresden | 3 | 293 | 330 | -2.98% | 8 | 36 | Township |
| Dresden | 4 | 293 | 327 | -2.98% | 8 | 36 | Township |
| Norcatur | 5 | 159 | 163 | -0.63% | 160 | 1 | City |
| Norcatur | 6 | 159 | 162 | -0.63% | 160 | 1 | City |
| Jennings | 7 | 105 | 108 | -0.94% | 3 | 36 | Township |
| Jennings | 8 | 105 | 108 | -0.94% | 3 | 36 | Township |
| Dresden | 9 | 98 | 102 | -1.01% | 3 | 36 | Township |
| Dresden | 10 | 98 | 102 | -1.01% | 3 | 36 | Township |
| Oberlin | 11 | 78 | 79 | 0% | 2 | 34 | Township |
| Oberlin | 12 | 78 | 79 | 0% | 2 | 34 | Township |
| Jennings | 13 | 78 | 81 | -1.27% | 291 | 0 | City |
| Jennings | 14 | 78 | 81 | -1.27% | 291 | 0 | City |
| Beaver | 15 | 64 | 66 | -1.54% | 2 | 36 | Township |
| Beaver | 16 | 64 | 66 | -1.54% | 2 | 36 | Township |
| Center | 17 | 52 | 54 | -1.89% | 1 | 36 | Township |
| Center | 18 | 52 | 54 | -1.89% | 1 | 36 | Township |
| Olive | 19 | 50 | 52 | -1.96% | 1 | 35 | Township |
| Olive | 20 | 50 | 52 | -1.96% | 1 | 35 | Township |
| Dresden | 21 | 42 | 44 | -2.33% | 47 | 1 | City |
| Dresden | 22 | 42 | 44 | -2.33% | 47 | 1 | City |
| Finley | 23 | 37 | 39 | -2.63% | 1 | 36 | Township |
| Finley | 24 | 37 | 39 | -2.63% | 1 | 36 | Township |
| Allison | 25 | 34 | 34 | 0% | 1 | 36 | Township |
| Allison | 26 | 34 | 34 | 0% | 1 | 36 | Township |
| Harlan | 27 | 34 | 36 | -2.86% | 1 | 36 | Township |
| Harlan | 28 | 34 | 36 | -2.86% | 1 | 36 | Township |
| Custer | 29 | 33 | 33 | 0% | 1 | 36 | Township |
| Custer | 30 | 33 | 33 | 0% | 1 | 36 | Township |
| Prairie Dog | 31 | 32 | 32 | 0% | 1 | 36 | Township |
| Prairie Dog | 32 | 32 | 32 | 0% | 1 | 36 | Township |
| Bassettville | 33 | 30 | 30 | 0% | 1 | 36 | Township |
| Bassettville | 34 | 30 | 30 | 0% | 1 | 36 | Township |
| Sappa | 35 | 22 | 22 | 0% | 1 | 36 | Township |
| Sappa | 36 | 22 | 22 | 0% | 1 | 36 | Township |
| Cook | 37 | 20 | 20 | 0% | 1 | 36 | Township |
| Cook | 38 | 20 | 20 | 0% | 1 | 36 | Township |
| Sherman | 39 | 19 | 19 | 0% | 1 | 36 | Township |
| Sherman | 40 | 19 | 19 | 0% | 1 | 36 | Township |
| Summit | 41 | 19 | 19 | 0% | 1 | 36 | Township |
| Summit | 42 | 19 | 19 | 0% | 1 | 36 | Township |
| Altory | 43 | 18 | 17 | 0% | 1 | 36 | Township |
| Altory | 44 | 18 | 17 | 0% | 1 | 36 | Township |
| Pleasant Valley | 45 | 17 | 17 | 0% | 0.00 | 36 | Township |
| Pleasant Valley | 46 | 17 | 17 | 0% | 0.00 | 36 | Township |
| Grant | 47 | 14 | 14 | 0% | 0.00 | 36 | Township |
| Grant | 48 | 14 | 14 | 0% | 0.00 | 36 | Township |
| Lyon | 49 | 13 | 13 | 0% | 0.00 | 36 | Township |
| Lyon | 50 | 13 | 13 | 0% | 0.00 | 36 | Township |
| Roosevelt | 51 | 12 | 12 | 0% | 0.00 | 36 | Township |
| Roosevelt | 52 | 12 | 12 | 0% | 0.00 | 36 | Township |
Oberlin is the largest city in Decatur County, with a population of 1,605.
Roosevelt is the smallest city in Decatur County, with a population of 12.
There are 52 cities in Decatur County, Kansas.