The California native will travel through her home state Friday on her return from Asia to support Newsom during the final weeks in the race to hold the governorship, her office told reporters.
Other prominent Democrats are also supportive.
Massachusetts Sen. Elizabeth Warren released a campaign ad last month that accused "Trump Republicans" of "coming to grab power" in California.
In her ad, she explained to voters that they will be receiving a mail-in ballot with just two questions on it – the first, whether Newsom should be recalled, and second, who should replace him.
Democrats across the U.S. have taken to social media to tell Californians to only vote "no" on their ballots and to leave the second section blank to avoid confusion.
Former communications director for both Newsom and Harris, Nathan Click, told voters in a tweet, "Voting NO is the only way ensure we don’t have a Trump Republican as Governor in one month’s time."
His message included a tweet that looked back at the state’s previous governor recall election in which Lt. Gov. Cruz Bustamante told California to vote "No on the Recall, Yes on Bustamante" – which some fear caused voter confusion.
Newsom also received the backing of President Biden.
"Gov. Gavin Newsom is leading California through unprecedented crises—he's a key partner in fighting the pandemic and helping build our economy back better," Biden said. "To keep him on the job, registered voters should vote no on the recall election by 9/14 and keep California moving forward."
If the majority of voters in California vote no on their ballots, Newsom will remain in office. The recall election is set for Sept. 14.
Newsom did not respond to Fox News' request for comment.
Fox News' Pat Ward contributed to this report.