It means a girl in 6th grade can ask for the HPV vaccine without letting her parents know.
The governor signed it without comment, posting it on the list of actions taken to "improve the health and wellbeing of Californians.
The law follows Center of Disease Control recommendations.
The CDC says girls should get the vaccine in order to protect them before they become sexually active. Nearly 70-percent of cervical cancers are linked to a strain of HPV that can be treated by vaccines, according to the CDC. The HPV vaccine involves three shots over a six month period.
Pediatrician Dr. Christine Halaburka says the bill is consistent with current law that allows access to birth control without parental consent. Halaburka adds that she doesn't expect to see any 12-year-old patients ask for the shots, but can see it benefiting older teens.
Parent Tracy LeBlanc says she can see the benefits of the HPV vaccine, but says 12 is too young to be making that kind of decision.
"I think its slowly stripping away parents' rights and as a parent I signed up to take care of my daughter until she's 18 and make all decisions about her medical care. But now the state has made this decision for me and I think that is wrong," LeBlanc said.
The new law takes effect in New Year's Day.