Smoking inside home day care centers would be banned under a bill targeting so-called "third-hand smoke" that lingers indoors.
The Assembly approved AB1819 on a 55-8 vote Monday, with some Republican lawmakers opposed.
The bill's author, Democratic Assemblyman Isadore Hall of Compton, says recent research shows that third-hand smoke can be a public health hazard.
Smoking already is banned in home day care centers during operating hours.
Supporters say the danger comes from smoke and cancer-causing compounds penetrating furniture, toys and other objects, which children will touch with their mouths.
Hall says day care providers can still smoke outside their homes if children are not with them.
California would join 12 other states that already ban smoking in home day cares. The bill now heads to the Senate.