19 cities
| City | County | 2026 Pop. ↓ |
|---|---|---|
| Kent | King County | 136,585 |
| Kirkland | King County | 96,878 |
| Kennewick | Benton County | 88,092 |
| Kenmore | King County | 24,302 |
| Kelso | Cowlitz County | 12,739 |
| Key Center | Kitsap County | 3,602 |
| Kalama | Cowlitz County | 3,210 |
| Kingston | Kitsap County | 2,697 |
| Kitsap Lake | Kitsap County | 2,313 |
| Kayak Point | Skagit County | 2,043 |
| Kettle Falls | Stevens County | 1,656 |
| Kittitas | Kittitas County | 1,441 |
| Kendall | Whatcom County | 953 |
| Klickitat | Klickitat County | 478 |
| Kapowsin | Pierce County | 476 |
| Keyport | Kitsap County | 207 |
| Keller | Ferry County | 186 |
| Kahlotus | Franklin County | 140 |
| Krupp | Adams County | 44 |