6 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Boise City | 1 | 238,443 | 236,043 | 0.2% | 2,769 | 86 | City |
| Meridian | 2 | 144,801 | 119,496 | 3.62% | 3,849 | 38 | City |
| Eagle | 3 | 33,913 | 31,603 | 1.38% | 737 | 46 | City |
| Kuna | 4 | 30,280 | 24,515 | 3.96% | 1,160 | 26 | City |
| Star | 5 | 19,893 | 11,466 | 9.25% | 1,686 | 12 | City |
| Garden City | 6 | 13,095 | 12,298 | 1.23% | 3,209 | 4 | City |
Boise City is the largest city in Ada County, with a population of 238,443.
Garden City is the smallest city in Ada County, with a population of 13,095.
There are 6 cities in Ada County, Idaho.