The one day walkout began at 7 a.m. Tuesday morning.
45 employees from the mental health and optical departments at Kaiser Fresno walked off the job.
They're represented by the National Union of Healthcare Workers. They joined about 1500 other Kaiser workers statewide to protest wage and benefit reductions they call unfair.
The healthcare provider says the nurses' union has not replied to their latest contract proposal.
All Kaiser campuses will be open throughout the strike, and temporary workers have been called in to replace striking employees.