Obama will appear with the three-term senator in Los Angeles on Oct. 22.
Earlier this year, he traveled to Los Angeles and San Francisco on separate occasions to raise cash for Boxer's re-election bid.
Boxer faces Republican Carly Fiorina, the former chief executive of Hewlett Packard, in the November election.
"It's terrific that President Obama will be coming to California to campaign with us as we enter the home stretch," Boxer campaign manager Rose Kapolczynski said in a statement.
Fiorina spokeswoman Andrea Saul called the trip Obama's "third attempted rescue mission to save the political life of a hyper partisan rubber stamp for the failed policies that are not bringing the 'help' and 'hope' they promised."
"Instead of working to stop the largest tax increase in U.S. history and to get more than 2. 2 million Californians back to work, President Obama and Barbara Boxer are working to save only one job - hers," Saul wrote in an e-mail.
Post updated at 10:51 p.m. with Fiorina campaign comment.
PHOTO CREDIT: President Barack Obama hugs Sen. Barbara Boxer, D-Calif., at a fundraiser for the Democratic National Committee and Sen. Barbara Boxer, D-Calif., at the California Science Center in Los Angeles, Monday, April 19, 2010.(AP Photo/ Alex Brandon)