30-year-old George Penca disappeared while hiking with members from his church group on Saturday.
The hikers say when they reached the end of the trail they divided up and returned to Yosemite Valley separately. But Penca never showed up.
Penca is five foot ten inches tall, weighs 240 pounds, and has dark brown hair and blue eyes.
Officials are asking anyone who may have seen Penca to call the search and rescue command post at (209) 372-0311.