22 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hermiston | 1 | 19,817 | 19,461 | 0.36% | 2,344 | 8 | City |
| Pendleton | 2 | 17,030 | 17,007 | 0.02% | 1,480 | 12 | City |
| Umatilla | 3 | 8,059 | 7,259 | 2.03% | 1,616 | 5 | City |
| Milton-Freewater | 4 | 6,987 | 7,106 | -0.34% | 3,444 | 2 | City |
| Stanfield | 5 | 2,111 | 2,145 | -0.33% | 1,222 | 2 | City |
| Walla Walla East | 6 | 1,864 | 2,459 | 0.65% | 833 | 2 | CDP |
| Pilot Rock | 7 | 1,307 | 1,334 | -0.46% | 884 | 1 | City |
| Athena | 8 | 1,180 | 1,197 | -0.34% | 2,149 | 1 | City |
| Mission | 9 | 1,021 | 888 | -0.1% | 134 | 8 | CDP |
| Weston | 10 | 702 | 715 | -0.43% | 1,307 | 1 | City |
| Green Meadows | 11 | 700 | 515 | 7.2% | 571 | 1 | CDP |
| Umapine | 12 | 666 | 537 | 3.58% | 201 | 3 | CDP |
| Echo | 13 | 624 | 636 | -0.48% | 1,080 | 1 | City |
| Adams | 14 | 388 | 390 | -0.26% | 1,093 | 0 | City |
| Gopher Flats | 15 | 385 | 327 | 0% | 183 | 2 | CDP |
| Tutuilla | 16 | 372 | 360 | -2.11% | 19 | 20 | CDP |
| Kirkpatrick | 17 | 258 | 223 | 2.38% | 72 | 4 | CDP |
| Ukiah | 18 | 235 | 173 | 5.38% | 1,059 | 0 | City |
| Helix | 19 | 191 | 193 | -0.52% | 1,504 | 0 | City |
| Meacham | 20 | 165 | 140 | 7.14% | 73 | 2 | CDP |
| McKay | 21 | 111 | 80 | 6.73% | 5 | 23 | CDP |
| Cayuse | 22 | 72 | 61 | 5.88% | 25 | 3 | CDP |
Hermiston is the largest city in Umatilla County, with a population of 19,817.
Cayuse is the smallest city in Umatilla County, with a population of 72.
There are 22 cities in Umatilla County, Oregon.