Willis, who co-wrote disco hits such as "Macho Man" and "In the Navy," was arrested in July after police found a gun and what was believed to be crack cocaine in his car after a traffic stop.
He was scheduled to be sentenced Thursday morning in San Mateo County Superior Court, but failed to show up. The judge issued arrest warrants for a probation violation and for the drug case, a clerk said.
Willis also had an outstanding felony warrant for possession of narcotics, police said.
His attorney, Kenneth Quigley, told the San Francisco Chronicle that Willis left a message with him Wednesday night saying he couldn't attend the hearing.
"He is scheduled for surgery. That's really as much as I know," Quigley told the newspaper.
The songwriter and performer left the Village People in the late 1970s.