Newsom said he will follow health guidelines and work remotely.
On Friday, he was at an event in San Francisco to announce a partnership with New Zealand Prime Minister Jacinda Ardern to address climate change.
"Grateful to be vaccinated & for treatments like Paxlovid," Newsom said, referring to the Pfizer medication taken orally to treat COVID.
Last September, two of Newsom's children tested positive for the virus. In a separate incident, he and his family went into quarantine in November after they were exposed to a California Highway Patrol officer who tested positive.