The law is expected to make lenders try harder to keep borrowers in their homes. Loan companies must prove they tried to modify the delinquent loans before they can begin foreclosing.
But supporters acknowledge the California Foreclosure Prevention Act won't stop thousands of foreclosures from eventually happening.
There have been more than 365,000 foreclosures in California since early 2007, with many more already scheduled.
The bill passed in February is similar to the Obama administration's Making Home Affordable Program that began in March.
Both encourages lenders to cut interest rates or rewrite loans to affordable levels.