San Jose Mayor Sam Liccardo is on board for Bloomberg.
More picks for the California team are expected in the coming weeks.
"Mayors don't have the luxury of hyper-partisan tongue wagging," Liccardo said in a statement. "They have to solve problems and get things done."
Liccardo said he's supporting Bloomberg because as the mayor of New York, he worked to reduce poverty, expand jobs, cut gun violence, improve public health and build affordable housing.
Liccardo had endorsed California Senator Kamala Harris but she withdrew from the race last week.