10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ontario | 1 | 12,004 | 11,767 | 0.39% | 2,018 | 6 | City |
| Nyssa | 2 | 3,283 | 3,211 | 0.43% | 2,118 | 2 | City |
| Vale | 3 | 2,095 | 1,903 | 1.85% | 1,801 | 1 | City |
| Riverside | 4 | 390 | 276 | 3.17% | 637 | 1 | CDP |
| Annex | 5 | 358 | 246 | 2.58% | 146 | 2 | CDP |
| Harper | 6 | 203 | 104 | 3.57% | 29 | 7 | CDP |
| Adrian | 7 | 161 | 155 | 0.63% | 660 | 0 | City |
| Jordan Valley | 8 | 139 | 134 | 0.72% | 67 | 2 | City |
| Juntura | 9 | 26 | 28 | 8.33% | 11 | 2 | CDP |
| Brogan | 10 | 20 | 21 | 5.26% | 7 | 3 | CDP |
Ontario is the largest city in Malheur County, with a population of 12,004.
Brogan is the smallest city in Malheur County, with a population of 20.
There are 10 cities in Malheur County, Oregon.