Organisers had collected 1.6 million verified signatures, surpassing the 1.5 million threshold needed by about 100,000.
Secretary of State Dr Shirley Weber said a recall election would be held unless a sufficient number of signatures are withdrawn within the next month.
“This now triggers the next phase of the recall process, a 30-business-day period in which voters may submit written requests to county Registrars of Voters to remove their names from the recall petition,” Ms Weber said in a statement.
Confirmation of the 1.5 million signatures comes just days after reality TV star Caitlyn Jenner officially announced her run for governor.
She will be one of Mr Newsom’s most high-profile opponents in a field that includes former San Diego Mayor Kevin Faulconer, businessman John Cox, who lost in 2018, and former Congressman Doug Ose.
In the election likely to go ahead in the fall, California voters must first decide whether Mr Newsom should be recalled, and if more than half say yes then their votes on who should replace him will decide the next governor.
That could still be Mr Newsom, who has already received “unambiguous” support from the White House in his campaign to fight the recall election.
Vice president Kamala Harris hit the stump with Mr Newsom in Oakland over the Easter holiday to offer the administration’s backing in the upcoming vote.
“We are unambiguous in our support for Governor Newsom,” Vice President Harris told The Chronicle, a California newspaper, about the White House position on the local recall effort.
Even if Mr Newsom does survive, however, he will face re-election in 2022 at what would have been the end of the four-year term that began in 2018, in which he received more than 60 per cent of the vote.
The last time Republicans took control of the heavy Democrat state was at another recall election in 2003, when actor Arnold Schwarzenegger replaced Gray Davis.
Veterans of that campaign have been hired by Ms Jenner in the hopes of repeating a Republican recall victory in 2021, including communications expert and former Trump campaign staffer Steven Cheung.
“For the past decade, we have seen the glimmer of the Golden State reduced by one-party rule that places politics over progress and special interests over people,” Ms Jenner wrote in her announcement press release.
Once a rising star of the party in control of that one-party state, Mr Newsom’s glimmer began to fade as his handling of the Covid pandemic became tainted with a dinner at the lavish French Laundry restaurant in violation of his own state guidelines.
Additional reporting by Associated Press
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