21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Hermiston | 1 | 19,518 | 19,445 | 0.08% | 2,309 | 8.45 | City |
| Pendleton | 2 | 17,467 | 17,021 | 0.51% | 1,518 | 11.51 | City |
| Umatilla | 3 | 8,004 | 7,381 | 1.59% | 1,605 | 4.99 | City |
| Milton-Freewater | 4 | 6,861 | 7,150 | -0.84% | 3,381 | 2.03 | City |
| Stanfield | 5 | 2,067 | 2,146 | -0.77% | 1,197 | 1.73 | City |
| Pilot Rock | 6 | 1,287 | 1,336 | -0.77% | 871 | 1.48 | City |
| Athena | 7 | 1,171 | 1,208 | -0.59% | 2,133 | 0.55 | City |
| Mission | 8 | 1,021 | 888 | -0.1% | 134 | 7.61 | CDP |
| Green Meadows | 9 | 700 | 515 | 7.2% | 571 | 1.23 | CDP |
| Weston | 10 | 689 | 716 | -0.72% | 1,283 | 0.54 | City |
| Umapine | 11 | 666 | 537 | 3.58% | 201 | 3.31 | CDP |
| Echo | 12 | 612 | 636 | -0.81% | 1,059 | 0.58 | City |
| Gopher Flats | 13 | 385 | 327 | 0% | 183 | 2.11 | CDP |
| Adams | 14 | 379 | 388 | -0.53% | 1,068 | 0.35 | City |
| Tutuilla | 15 | 372 | 360 | -2.1% | 19 | 20 | CDP |
| Kirkpatrick | 16 | 258 | 223 | 2.38% | 72 | 3.58 | CDP |
| Helix | 17 | 188 | 193 | -0.53% | 1,480 | 0.13 | City |
| Ukiah | 18 | 168 | 167 | 0% | 757 | 0.22 | City |
| Meacham | 19 | 165 | 140 | 7.14% | 73 | 2.27 | CDP |
| McKay | 20 | 111 | 80 | 6.73% | 5 | 23.44 | CDP |
| Cayuse | 21 | 72 | 61 | 5.88% | 25 | 2.88 | CDP |
Hermiston is the largest city in Umatilla County, with a population of 19,518.
Cayuse is the smallest city in Umatilla County.
There are 21 cities in Umatilla County, Oregon.