The new law states that animals must be obtained from an animal shelter and the store must post the name of the agency where it got the animal; no breeders will be allowed.
The change comes from the Pet Rescue and Adoption Act, which was signed into law by Gov. Jerry Brown in October 2017.
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The law requires the stores to keep public records that show where each dog, cat or rabbit came from. A violation would mean a $500 fine.
Thirty-six cities in California, including Sacramento, Los Angeles and San Francisco already had similar bans in place, but no statewide bans existed.
"Californians spend more than $250 million a year to house and euthanize animals in our shelters," O'Donnell said in a statement to the Associated Press. "Protecting the pets that make our house a home is an effort that makes us all proud."
Those looking to purchase a new furry friend still have the option to buy from a private breeder.