39 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Clear Creek | 1 | 38,825 | 36,417 | 0.78% | 848 | 46 | Township |
| Mason | 2 | 36,626 | 34,886 | 0.8% | 1,880 | 19 | City |
| Franklin | 3 | 33,583 | 31,677 | 0.86% | 1,020 | 33 | Township |
| Lebanon | 4 | 22,553 | 20,879 | 1.25% | 1,674 | 13 | City |
| Springboro | 5 | 19,900 | 19,137 | 0.64% | 2,161 | 9 | City |
| Turtlecreek | 6 | 18,395 | 17,746 | 1.04% | 305 | 60 | Township |
| Franklin | 7 | 11,793 | 11,688 | 0.15% | 1,253 | 9 | City |
| Franklin | 8 | 11,211 | 11,432 | 0.16% | 1,644 | 7 | Township |
| South Lebanon | 9 | 7,152 | 6,464 | 1.63% | 2,086 | 3 | Village |
| Union | 10 | 6,889 | 6,286 | 1.22% | 517 | 13 | Township |
| Franklin | 11 | 6,439 | 6,289 | 0.47% | 515 | 13 | Township |
| Harlan | 12 | 5,407 | 4,951 | 1.14% | 119 | 45 | Township |
| Franklin | 13 | 4,711 | 4,824 | -0.59% | 205 | 23 | Township |
| Franklin | 14 | 4,245 | 4,236 | 0.09% | 118 | 36 | Township |
| Franklin | 15 | 3,783 | 3,607 | 0.96% | 96 | 39 | Township |
| Franklin | 16 | 3,511 | 3,491 | 0.37% | 142 | 25 | Township |
| Washington | 17 | 3,036 | 2,770 | 1.23% | 90 | 34 | Township |
| Waynesville | 18 | 2,953 | 2,679 | 1.58% | 1,250 | 2 | Village |
| Franklin | 19 | 2,634 | 2,508 | 0.84% | 106 | 25 | Township |
| Franklin | 20 | 2,311 | 2,302 | 0.22% | 63 | 37 | Township |
| Morrow | 21 | 2,267 | 2,063 | 1.52% | 1,113 | 2 | Village |
| Franklin | 22 | 2,223 | 2,130 | 0.54% | 91 | 25 | Township |
| Franklin | 23 | 1,762 | 1,702 | 1.09% | 66 | 27 | Township |
| Franklin | 24 | 1,694 | 1,710 | -0.18% | 80 | 21 | Township |
| Franklin | 25 | 1,658 | 1,616 | 0.55% | 60 | 27 | Township |
| Maineville | 26 | 1,567 | 1,416 | 1.62% | 987 | 2 | Village |
| Franklin | 27 | 1,421 | 1,448 | -0.42% | 41 | 35 | Township |
| Massie | 28 | 1,290 | 1,190 | 1.26% | 70 | 18 | Township |
| Franklin | 29 | 1,192 | 1,151 | 0.68% | 49 | 24 | Township |
| Franklin | 30 | 1,174 | 1,186 | 0% | 47 | 25 | Township |
| Franklin | 31 | 1,045 | 1,037 | 0.29% | 19 | 54 | Township |
| Mason | 32 | 939 | 986 | -0.63% | 24 | 39 | Township |
| Lebanon | 33 | 862 | 902 | -1.15% | 24 | 36 | Township |
| Franklin | 34 | 738 | 759 | -0.27% | 32 | 23 | Township |
| Franklin | 35 | 673 | 686 | 0% | 23 | 29 | Township |
| Harveysburg | 36 | 591 | 555 | 1.03% | 595 | 1 | Village |
| Franklin | 37 | 513 | 540 | -0.97% | 25 | 20 | Township |
| Franklin | 38 | 353 | 370 | -1.12% | 15 | 24 | Township |
| Pleasant Plain | 39 | 144 | 129 | 2.13% | 889 | 0 | Village |
Clear Creek is the largest city in Warren County, with a population of 38,825.
Pleasant Plain is the smallest city in Warren County, with a population of 144.
There are 39 cities in Warren County, Ohio.