19 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Kent | King County | 136,586 |
| Kirkland | King County | 96,188 |
| Kennewick | Benton County | 87,410 |
| Kenmore | King County | 24,234 |
| Kelso | Cowlitz County | 12,738 |
| Key Center | Kitsap County | 3,608 |
| Kalama | Cowlitz County | 3,170 |
| Kingston | Kitsap County | 2,660 |
| Kitsap Lake | Kitsap County | 2,168 |
| Kayak Point | Skagit County | 1,915 |
| Kettle Falls | Stevens County | 1,652 |
| Kittitas | Kittitas County | 1,443 |
| Kendall | Whatcom County | 905 |
| Klickitat | Klickitat County | 470 |
| Kapowsin | Pierce County | 467 |
| Keyport | Kitsap County | 229 |
| Keller | Ferry County | 189 |
| Kahlotus | Franklin County | 140 |
| Krupp | Adams County | 44 |