9 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Boise City | 1 | 238,443 | 236,043 | 0.2% | 2,820 | 85 | City |
| Meridian | 2 | 144,801 | 119,496 | 3.62% | 3,929 | 37 | City |
| Eagle | 3 | 33,913 | 31,603 | 1.38% | 1,045 | 32 | City |
| Kuna | 4 | 30,280 | 24,515 | 3.96% | 1,179 | 26 | City |
| Star | 5 | 19,893 | 11,466 | 9.25% | 2,046 | 10 | City |
| Garden City | 6 | 13,095 | 12,298 | 1.23% | 3,209 | 4 | City |
| Hidden Springs | 7 | 3,910 | 3,416 | 2.87% | 1,484 | 3 | CDP |
| Avimor | 8 | 1,642 | 1,211 | 7.11% | 1,206 | 1 | CDP |
| Robie Creek | 9 | 1,256 | 1,380 | 0.48% | 42 | 30 | CDP |
Boise City is the largest city in Ada County, with a population of 238,443.
Robie Creek is the smallest city in Ada County, with a population of 1,256.
There are 9 cities in Ada County, Idaho.