Smoking during day care hours is already banned. The new law is intended to eliminate health risks from "third hand smoke" which lingers in furniture and carpets.
Operators at 36,000 private family day care homes face penalties of $100 and license revocation if they violate the law.
Ashlee Chen operates a state licensed in-home daycare service in Sacramento. She supports the law.
"We're supposed to be providing good health to children and this smoke gets stuck on the couch, on the clothes, everything. So we're not really providing a healthy environment if it smells of smoke all the time."
The new law allows cities or counties to enact or enforce ordinances relating to smoking in a family day care home if the local ordinance is more stringent than the state law.