6 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Boise City | 1 | 238,923 | 236,043 | 0.2% | 2,775 | 86 | City |
| Meridian | 2 | 149,862 | 119,496 | 3.5% | 3,984 | 38 | City |
| Eagle | 3 | 34,375 | 31,603 | 1.36% | 747 | 46 | City |
| Kuna | 4 | 31,433 | 24,515 | 3.81% | 1,204 | 26 | City |
| Star | 5 | 21,579 | 11,466 | 8.48% | 1,828 | 12 | City |
| Garden City | 6 | 13,255 | 12,298 | 1.22% | 3,248 | 4 | City |
Boise City is the largest city in Ada County, with a population of 238,923.
Garden City is the smallest city in Ada County, with a population of 13,255.
There are 6 cities in Ada County, Idaho.