Project Survival's Cat Haven in Dunlap, about 40 miles east of Fresno, said the lion was a 4-year-old male, KMPH.com reported. The animal had been living in the sanctuary in the foothills of the Sierra Nevada Mountains since it was 8 months old.
The worker was in a cage with the lion when it attacked, police said. Fresno County sheriff's deputies killed the lion.
Cat Haven, which opened in 1993, provides a home for lions, tigers and other large cats.