Those found breaking the law could face a fine of $500 (£395) or in repeat cases, $1,000.
"We applaud Gov Newsom and the state's lawmakers for recognising that California citizens do not want their state's markets to contribute to the demand for fur products," a statement from Humane Society USA said.
But the decision was criticised by the Fur Information Council's spokesman Keith Kaplan. He claimed it was part of a "radical vegan agenda using fur as the first step to other bans on what we wear and eat."
Last May, fashion house Prada announced that it would stop using fur, starting with its spring-summer 2020 line.