10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ontario | 1 | 11,949 | 11,741 | 0.35% | 2,009 | 5.95 | City |
| Nyssa | 2 | 3,281 | 3,211 | 0.43% | 2,117 | 1.55 | City |
| Vale | 3 | 1,952 | 1,904 | 0.51% | 1,678 | 1.16 | City |
| Riverside | 4 | 390 | 276 | 3.17% | 637 | 0.61 | CDP |
| Annex | 5 | 358 | 246 | 2.58% | 146 | 2.46 | CDP |
| Harper | 6 | 203 | 104 | 3.57% | 29 | 7 | CDP |
| Adrian | 7 | 157 | 152 | 0.64% | 643 | 0.24 | City |
| Jordan Valley | 8 | 140 | 135 | 0.72% | 67 | 2.08 | City |
| Juntura | 9 | 26 | 28 | 8.33% | 11 | 2.29 | CDP |
| Brogan | 10 | 20 | 21 | 5.26% | 7 | 2.86 | CDP |
Ontario is the largest city in Malheur County, with a population of 11,949.
Brogan is the smallest city in Malheur County.
There are 10 cities in Malheur County, Oregon.