The strike formally ended at 4 a.m. Thousands of hospital pharmacists, nursing assistants, operating room assistants and other health care workers walked out of their jobs.
The union representing health care workers said the strike was over low staffing levels, but UC officials say the issue is a reduced benefit pension offer.
Dozens of surgeries had to be postponed during the strike. Nearly 450 union employees remained in critical jobs under a court order. No major problems were reported.
Hospital administrators say they assured good care for patients at facilities in San Diego, Orange, Los Angeles, Santa Monica, San Francisco and Sacramento.
The Associated Press contributed to this report.