16 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fairbury | 1 | 3,829 | 3,964 | -0.75% | 1,510 | 3 | City |
| Fairbury | 2 | 3,829 | 3,973 | -0.75% | 1,510 | 3 | City |
| Plymouth | 3 | 365 | 364 | 0% | 1,155 | 0 | Village |
| Plymouth | 4 | 365 | 365 | 0% | 1,155 | 0 | Village |
| Diller | 5 | 270 | 248 | 1.5% | 640 | 0 | Village |
| Diller | 6 | 270 | 249 | 1.5% | 640 | 0 | Village |
| Daykin | 7 | 153 | 155 | -0.65% | 933 | 0 | Village |
| Daykin | 8 | 153 | 156 | -0.65% | 933 | 0 | Village |
| Endicott | 9 | 113 | 113 | 0% | 247 | 0 | Village |
| Endicott | 10 | 113 | 113 | 0% | 247 | 0 | Village |
| Jansen | 11 | 100 | 100 | 0% | 319 | 0 | Village |
| Jansen | 12 | 100 | 100 | 0% | 319 | 0 | Village |
| Harbine | 13 | 51 | 53 | -1.92% | 486 | 0 | Village |
| Harbine | 14 | 51 | 53 | -1.92% | 486 | 0 | Village |
| Steele City | 15 | 49 | 51 | -2% | 210 | 0 | Village |
| Steele City | 16 | 49 | 51 | -2% | 210 | 0 | Village |
Fairbury is the largest city in Jefferson County, with a population of 3,829.
Steele City is the smallest city in Jefferson County, with a population of 49.
There are 16 cities in Jefferson County, Nebraska.