14 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Oakland | 1 | 444,839 | 440,983 | 0.14% | 7,949 | 56 | City |
| Fremont | 2 | 227,065 | 230,445 | -0.25% | 2,907 | 78 | City |
| Hayward | 3 | 156,297 | 162,726 | -0.68% | 3,411 | 46 | City |
| Berkeley | 4 | 120,514 | 124,219 | -0.51% | 11,552 | 10 | City |
| San Leandro | 5 | 84,493 | 90,727 | -1.21% | 6,342 | 13 | City |
| Livermore | 6 | 83,363 | 87,875 | -0.89% | 3,137 | 27 | City |
| Alameda | 7 | 79,134 | 78,117 | 0.22% | 7,610 | 10 | City |
| Pleasanton | 8 | 73,660 | 79,671 | -1.34% | 3,051 | 24 | City |
| Dublin | 9 | 69,675 | 72,281 | -0.62% | 4,575 | 15 | City |
| Union City | 10 | 64,327 | 69,933 | -1.43% | 3,316 | 19 | City |
| Newark | 11 | 45,623 | 47,516 | -0.69% | 3,278 | 14 | City |
| Albany | 12 | 19,045 | 20,226 | -1.02% | 10,640 | 2 | City |
| Emeryville | 13 | 14,407 | 12,921 | 1.75% | 11,317 | 1 | City |
| Piedmont | 14 | 10,595 | 11,258 | -1.03% | 6,232 | 2 | City |
Oakland is the largest city in Alameda County, with a population of 444,839.
Piedmont is the smallest city in Alameda County, with a population of 10,595.
There are 14 cities in Alameda County, California.