| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Mason | 1 | 36,088 | 34,882 | 0.71% | 1,852 | 19 | City |
| Lebanon | 2 | 22,360 | 20,867 | 1.13% | 1,659 | 13 | City |
| Springboro | 3 | 19,709 | 19,136 | 0.53% | 2,140 | 9 | City |
| Franklin | 4 | 11,648 | 11,676 | 0.01% | 1,238 | 9 | City |
| South Lebanon | 5 | 7,070 | 6,455 | 1.51% | 2,062 | 3 | Village |
| Waynesville | 6 | 2,930 | 2,687 | 1.38% | 1,240 | 2 | Village |
| Morrow | 7 | 2,254 | 2,061 | 1.39% | 1,107 | 2 | Village |
| Maineville | 8 | 1,541 | 1,405 | 1.52% | 970 | 2 | Village |
| Harveysburg | 9 | 582 | 551 | 0.87% | 586 | 1 | Village |
| Pleasant Plain | 10 | 142 | 129 | 1.43% | 877 | 0 | Village |
Mason is the largest city in Warren County, with a population of 36,088.
Pleasant Plain is the smallest city in Warren County, with a population of 142.
There are 10 cities in Warren County, Ohio.