| City | County | 2025 Pop. ↓ |
|---|---|---|
| Kent | King County | 131,235 |
| Kirkland | King County | 90,164 |
| Kennewick | Benton County | 85,940 |
| Kenmore | King County | 23,057 |
| Kelso | Cowlitz County | 12,592 |
| Key Center | Kitsap County | 3,276 |
| Kingston | Kitsap County | 3,224 |
| Kalama | Cowlitz County | 3,073 |
| Kitsap Lake | Kitsap County | 2,567 |
| Kayak Point | Skagit County | 2,076 |
| Kettle Falls | Stevens County | 1,670 |
| Kittitas | Kittitas County | 1,435 |
| Kendall | Whatcom County | 1,151 |
| Kapowsin | Pierce County | 389 |
| Klickitat | Klickitat County | 328 |
| Keller | Ferry County | 261 |
| Keyport | Kitsap County | 216 |
| Kahlotus | Franklin County | 135 |
| Krupp | Adams County | 47 |