9 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Boise City | 1 | 235,012 | 236,034 | -0.09% | 2,779 | 84.55 | City |
| Meridian | 2 | 145,039 | 119,443 | 3.66% | 3,935 | 36.86 | City |
| Eagle | 3 | 33,285 | 30,870 | 1.47% | 1,025 | 32.46 | City |
| Kuna | 4 | 30,427 | 24,484 | 4.07% | 1,185 | 25.68 | City |
| Star | 5 | 19,590 | 11,447 | 9.07% | 2,014 | 9.72 | City |
| Garden City | 6 | 13,110 | 12,295 | 1.26% | 3,212 | 4.08 | City |
| Hidden Springs | 7 | 3,910 | 3,416 | 2.87% | 1,484 | 2.63 | CDP |
| Avimor | 8 | 1,642 | 1,211 | 7.11% | 1,206 | 1.36 | CDP |
| Robie Creek | 9 | 1,256 | 1,380 | 0.48% | 42 | 30.09 | CDP |
Boise City is the largest city in Ada County, with a population of 235,012.
Robie Creek is the smallest city in Ada County.
There are 9 cities in Ada County, Idaho.