7 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fort Atkinson | 1 | 12,326 | 12,579 | -0.41% | 2,108 | 6 | City |
| Jefferson | 2 | 7,761 | 7,784 | -0.06% | 1,331 | 6 | City |
| Lake Mills | 3 | 6,705 | 6,265 | 1.33% | 1,605 | 4 | City |
| Waterloo | 4 | 3,639 | 3,496 | 0.78% | 959 | 4 | City |
| Johnson Creek | 5 | 3,412 | 3,341 | 0.41% | 1,127 | 3 | Village |
| Palmyra | 6 | 1,717 | 1,727 | -0.12% | 749 | 2 | Village |
| Sullivan | 7 | 653 | 652 | 0% | 576 | 1 | Village |
Fort Atkinson is the largest city in Jefferson County, with a population of 12,326.
Sullivan is the smallest city in Jefferson County, with a population of 653.
There are 7 cities in Jefferson County, Wisconsin.