Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hillsboro | 1 | 107,976 | 106,990 | 0.23% | 4,178 | 25.8 | City |
| Beaverton | 2 | 96,756 | 97,510 | -0.19% | 4,926 | 19.6 | City |
| Tigard | 3 | 55,781 | 55,017 | 0.34% | 4,373 | 12.8 | City |
| Aloha | 4 | 54,216 | 53,724 | 0.64% | 7,370 | 7.4 | CDP |
| Tualatin | 5 | 27,216 | 27,884 | -0.61% | 3,241 | 8.4 | City |
| Forest Grove | 6 | 26,988 | 26,231 | 0.7% | 4,581 | 5.9 | City |
| Sherwood | 7 | 19,801 | 20,424 | -0.78% | 4,046 | 4.9 | City |
| Cornelius | 8 | 15,710 | 12,792 | 4.87% | 6,717 | 2.3 | City |
| Oak Hills | 9 | 11,854 | 11,682 | 0.31% | 7,623 | 1.6 | CDP |
| Cedar Hills | 10 | 9,205 | 9,514 | 0.7% | 4,883 | 1.9 | CDP |
| Garden Home-Whitford | 11 | 7,155 | 7,295 | 0.49% | 4,619 | 1.5 | CDP |
| Raleigh Hills | 12 | 6,877 | 6,675 | 1.03% | 4,521 | 1.5 | CDP |
| West Slope | 13 | 6,681 | 6,799 | 0.14% | 4,134 | 1.6 | CDP |
| Marlene Village | 14 | 6,167 | 5,356 | 7.7% | 6,747 | 0.9 | CDP |
| King City | 15 | 4,898 | 5,176 | -1.41% | 6,039 | 0.8 | City |
| Metzger | 16 | 3,960 | 4,402 | 0.36% | 5,211 | 0.8 | CDP |
| North Plains | 17 | 3,356 | 3,443 | -0.65% | 3,079 | 1.1 | City |
| Durham | 18 | 1,833 | 1,941 | -1.45% | 4,471 | 0.4 | City |
| Banks | 19 | 1,796 | 1,839 | -0.61% | 2,357 | 0.8 | City |
| Gaston | 20 | 663 | 677 | -0.6% | 1,944 | 0.3 | City |
| Cherry Grove | 21 | 570 | 506 | 7.55% | 527 | 1.1 | CDP |
| Dilley | 22 | 285 | 172 | 7.95% | 381 | 0.7 | CDP |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Hillsboro is the largest city in Washington County.
Dilley is the smallest city in Washington County.
There are 22 cities in Washington County, Oregon.