Jesus Hernandez Tobar, 30, was advised of the three felony charges against him -- assault with intent to commit rape and two counts of sexual battery -- Chief Deputy District Attorney Michael O' Reilley said.
Deputy Public Defender Courtaney Ann Wilson was appointed to represent Tobar, who will be arraigned on Wednesday morning, O' Reilley said. Tobar was arrested by Napa State Police and is being held in Napa County Jail under $250,000 bail.
O'Reilley would not comment about the circumstances of the alleged attack.
It's the third reported act of violence at the hospital since October.
Napa State Hospital psychiatric technician Donna Gross, 54, of Concord, was murdered by a patient at the hospital on Oct. 23. A preliminary hearing for the accused killer, Jess Willard Massey, 37, is scheduled for May 2.
George Anderson, 60, a rehabilitation therapist, suffered multiple fractures when he was attacked at the hospital on Dec. 11. His alleged assailant, Sean Bouchie, 24, was found incompetent to stand trial and was sent back to Napa State Hospital.
Napa State Hospital employees and their union representatives have rallied and protested against what they say are unsafe conditions at the hospital and inadequate staffing.
"It just shows that the violence there is pervasive and there should be increased police presence there," Dr. Stuart Bussey, president of the Union of American Physicians and Dentists, said in a statement Thursday.