22 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Oakland | 1 | 444,196 | 440,983 | 0.14% | 7,937 | 56 | City |
| Fremont | 2 | 227,628 | 230,445 | -0.25% | 2,914 | 78 | City |
| Hayward | 3 | 157,368 | 162,726 | -0.68% | 3,435 | 46 | City |
| Berkeley | 4 | 121,131 | 124,219 | -0.51% | 11,611 | 10 | City |
| San Leandro | 5 | 85,532 | 90,727 | -1.2% | 6,420 | 13 | City |
| Livermore | 6 | 84,115 | 87,875 | -0.89% | 3,166 | 27 | City |
| Alameda | 7 | 78,964 | 78,117 | 0.21% | 7,593 | 10 | City |
| Pleasanton | 8 | 74,662 | 79,671 | -1.32% | 3,093 | 24 | City |
| Dublin | 9 | 70,109 | 72,281 | -0.62% | 4,604 | 15 | City |
| Castro Valley | 10 | 66,458 | 64,392 | 0.51% | 3,945 | 17 | CDP |
| Union City | 11 | 65,261 | 69,933 | -1.41% | 3,364 | 19 | City |
| Newark | 12 | 45,938 | 47,516 | -0.68% | 3,300 | 14 | City |
| San Lorenzo | 13 | 31,336 | 30,117 | 1.71% | 10,288 | 3 | CDP |
| Mountain House | 14 | 27,069 | 21,387 | 4.48% | 5,939 | 5 | CDP |
| Ashland | 15 | 23,474 | 23,566 | 0.45% | 12,737 | 2 | CDP |
| Albany | 16 | 19,242 | 20,226 | -1.01% | 10,750 | 2 | City |
| Cherryland | 17 | 15,692 | 15,976 | 0.41% | 13,153 | 1 | CDP |
| Emeryville | 18 | 14,159 | 12,921 | 1.78% | 11,123 | 1 | City |
| Fairview | 19 | 10,728 | 10,834 | 0.45% | 3,607 | 3 | CDP |
| Piedmont | 20 | 10,705 | 11,258 | -1.03% | 6,297 | 2 | City |
| Kensington | 21 | 5,367 | 5,171 | 0.36% | 5,567 | 1 | CDP |
| Sunol | 22 | 922 | 835 | 0.11% | 33 | 28 | CDP |
Oakland is the largest city in Alameda County, with a population of 444,196.
Sunol is the smallest city in Alameda County, with a population of 922.
There are 22 cities in Alameda County, California.