Mental health workers with the National Union of Healthcare Workers are planning a week of strikes against Kaiser Permanente starting Monday.
Union officials said it will be the largest mental health worker strike in U.S. history.
Some 2,600 clinicians are planning to walk out because they say Kaiser is failing to provide timely and adequate care to patients.
"For patients suffering from depression, anxiety and other debilitating mental conditions, these delays can be insurmountable obstacles, sometimes leading to tragic outcomes," said Clement Papazian, president of the union's Northern California chapter of mental health clinicians.
Another 700 Kaiser workers, including medical social workers and registered dieticians, are planning to participate in the strike to protest
problems with inadequate staffing, union officials said.
In November, nurses at Kaiser Permanente went on strike because they said patient care standards had eroded at the HMO.
Union workers are planning to establish 65 picket lines and strike at 35 locations across California.
In the Bay Area, the union is planning to strike in San Francisco, San Jose, Santa Rosa, San Leandro, Richmond, Oakland and other locations.