Officials in the county of Santa Clara, voted to enact the ban to fight an "obesity epidemic" sweeping California and the US.
"This ordinance prevents restaurants from preying on children's love of toys to peddle high-calorie, high-fat, high-sodium kids meals," said Ken Yeager, the county supervisor behind the ban.
"This ordinance breaks the link between unhealthy food and prizes."
The ban will take effect in 90 days unless major fast-food chains and the state restaurateurs association successfully pitch a better solution.
It will bar toys from being offered with meals that don't meet a set of basic nutrition standards.