28 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hanover | 1 | 21,253 | 18,330 | 1.96% | 739 | 29 | Township |
| Madison | 2 | 17,815 | 18,062 | -0.2% | 310 | 57 | Township |
| Madison | 3 | 12,051 | 12,336 | -0.47% | 1,395 | 9 | City |
| Madison | 4 | 10,427 | 10,193 | 0.81% | 379 | 28 | Township |
| Hanover | 5 | 5,669 | 5,576 | 0.35% | 303 | 19 | Township |
| Hanover | 6 | 3,848 | 3,741 | 0.55% | 1,733 | 2 | Town |
| Madison | 7 | 3,016 | 3,027 | -0.03% | 82 | 37 | Township |
| Madison | 8 | 2,862 | 2,911 | -0.42% | 82 | 35 | Township |
| Hanover | 9 | 2,209 | 2,222 | 0.5% | 81 | 27 | Township |
| Madison | 10 | 2,123 | 2,129 | 0.14% | 83 | 26 | Township |
| Madison | 11 | 1,791 | 1,788 | -0.06% | 34 | 52 | Township |
| Madison | 12 | 1,730 | 1,661 | 0.99% | 47 | 37 | Township |
| Republican | 13 | 1,624 | 1,629 | 0.06% | 59 | 27 | Township |
| Graham | 14 | 1,564 | 1,583 | -0.13% | 37 | 42 | Township |
| Lancaster | 15 | 1,463 | 1,480 | -0.27% | 45 | 32 | Township |
| Saluda | 16 | 1,382 | 1,367 | 0.29% | 37 | 37 | Township |
| Madison | 17 | 1,280 | 1,281 | 0.31% | 29 | 45 | Township |
| Madison | 18 | 1,188 | 1,162 | 0.25% | 33 | 36 | Township |
| Madison | 19 | 1,125 | 1,074 | 0.9% | 32 | 35 | Township |
| Smyrna | 20 | 1,082 | 1,094 | -0.09% | 42 | 26 | Township |
| Madison | 21 | 671 | 658 | 1.05% | 26 | 26 | Township |
| Madison | 22 | 640 | 634 | 0.63% | 21 | 31 | Township |
| Madison | 23 | 462 | 448 | 1.09% | 22 | 21 | Township |
| Madison | 24 | 355 | 362 | 0% | 16 | 22 | Township |
| Dupont | 25 | 337 | 341 | -0.3% | 334 | 1 | Town |
| Canaan | 26 | 163 | 70 | 7.24% | 578 | 0 | CDP |
| Brooksburg | 27 | 69 | 72 | -1.43% | 676 | 0 | Town |
| Deputy | 28 | 24 | 34 | 9.09% | 324 | 0 | CDP |
Hanover is the largest city in Jefferson County, with a population of 21,253.
Deputy is the smallest city in Jefferson County, with a population of 24.
There are 28 cities in Jefferson County, Indiana.