I’ve decided not to run for US Senate, my heart and family are in CA. But our work is not done and neither am I. http://t.co/DJH7U8eNfG— Antonio Villaraigosa (@villaraigosa) February 24, 2015
"As I think about how best to serve the people of this great state, I know that my heart and my family are here in California, not Washington, D.C.," Villaraigosa said in a statement posted on Facebook.
Billionaire climate activist Tom Steyer has also opted not to run for Senate, which leaves state Attorney General Kamala Harris as the only major candidate in the contest after Boxer announced in January that she would not seek re-election in 2016.
Harris has rolled out hard-to-miss endorsements from Los Angeles municipal unions.
Villaraigosa, 62, did not say whether he plans to run for governor.
Lt. Gov. Gavin Newsom also weighed a run for Boxer's seat but then announced plans to run for governor.
The Associated Press and City News Service contributed to this report.