| City / Town | 2020 Census | 2025 estimate |
|---|---|---|
| San Rafael | 61,278 | 59,410 |
| Novato | 53,206 | 51,947 |
| Mill Valley | 14,233 | 13,799 |
| Larkspur | 13,058 | 12,620 |
| San Anselmo | 12,831 | 12,555 |
| Corte Madera | 10,221 | 9,929 |
| Tiburon | 9,162 | 8,881 |
| Fairfax | 7,603 | 7,417 |
| Sausalito | 7,268 | 7,019 |
| Ross | 2,336 | 2,304 |
| Belvedere | 2,131 | 2,066 |
| Marin County total | 262,321 | 253,694 |
Source: U.S. Census Bureau via citypopulation.de; county total from Census QuickFacts.
Every incorporated town lost population between 2020 and 2025. Countywide, the population fell 3.3% over that period.
About 69,000 residents, roughly a quarter of the county, live in unincorporated communities such as Kentfield, Strawberry, Tamalpais Valley, Lucas Valley–Marinwood, Santa Venetia and Marin City (2,993 residents in 2020). For those areas, the County of Marin, not a city, handles zoning and permits.
