17 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ellensburg | 1 | 20,838 | 21,557 | -0.75% | 2,504 | 8 | City |
| Ellensburg | 2 | 20,838 | 21,627 | -0.75% | 2,504 | 8 | City |
| Terrace Heights | 3 | 10,492 | 8,917 | 2.31% | 998 | 11 | CDP |
| Union Gap | 4 | 6,589 | 6,568 | 0.11% | 1,181 | 6 | City |
| Union Gap | 5 | 6,589 | 6,553 | 0.11% | 1,181 | 6 | City |
| Cle Elum | 6 | 2,300 | 2,159 | 1.05% | 512 | 4 | City |
| Cle Elum | 7 | 2,300 | 2,177 | 1.05% | 512 | 4 | City |
| Kittitas | 8 | 1,443 | 1,446 | -0.14% | 1,848 | 1 | City |
| Kittitas | 9 | 1,443 | 1,453 | -0.14% | 1,848 | 1 | City |
| Roslyn | 10 | 959 | 955 | -0.1% | 218 | 4 | City |
| Roslyn | 11 | 959 | 961 | -0.1% | 218 | 4 | City |
| South Cle Elum | 12 | 574 | 560 | 0.35% | 1,428 | 0 | Town |
| South Cle Elum | 13 | 574 | 561 | 0.35% | 1,428 | 0 | Town |
| Snoqualmie Pass | 14 | 447 | 395 | 2.05% | 153 | 3 | CDP |
| Easton | 15 | 290 | 302 | -4.29% | 90 | 3 | CDP |
| Ronald | 16 | 237 | 202 | -2.07% | 256 | 1 | CDP |
| Thorp | 17 | 52 | 109 | -20% | 43 | 1 | CDP |
Ellensburg is the largest city in Kittitas County, with a population of 20,838.
Thorp is the smallest city in Kittitas County, with a population of 52.
There are 17 cities in Kittitas County, Washington.