Jose Rafael Guzman, 27, of Huntington Park, was charged with criminal threats and threatening a public officer, Long Beach police said.
"We take all potential threats of violence very seriously and thoroughly investigate all reported incidents," Chief Robert Luna said in a statement. "Our department will remain vigilant and continue to be visible to ensure the safety of our community."
The details of the alleged threat were unclear. Police said they were notified about the threat by "a concerned community member."
Police said Guzman was booked into the Long Beach City jail and was released after posting $50,000 bail.
When reached for comment by Fox News, Sanders' campaign said it would "not comment on matters of security."
Long Beach police said they had scheduled extra patrols in high visibility areas and vowed to "place all available resources in high visibility areas" following a pair of mass shootings in the U.S. over the weekend.
The Sanders rally is scheduled to take place Tuesday evening at Long Beach City College.
Fox News' Tara Prindiville contributed to this report.
The Associated Press contributed to this report.