George Penca, 30, has been missing since Friday when he became separated from his church group during a hike.
Relatives said Penca wasn't carrying a cellphone when he disappeared. He was wearing a black T-shirt and gray sweatpants when he was last seen.
The Hawthorne man had gone on a day hike with about 20 members of his church. The group was on the Upper Yosemite Fall trail late in the afternoon when relatives say Penca decided to turn back.
"They went two separate groups, and he wasn't feeling so good, so he wanted to go back. From what I understand, he took the wrong trail back," said Teresa Mundo, Penca's cousin. "They all thought they were going to meet up with him. That's when they reported him missing."
Mundo said the family is very worried about Penca.
"I am very nervous. He's not experienced in hiking," said Mundo. "There are mountain lions out there. Is he sleeping OK? Is he dehydrated? Is he starving? Everything is going through my mind."
Search and rescue teams are combing the park. Yosemite officials said Penca disappeared on a trail that is popular and well-maintained.
Relatives said Penca was very active at his church in Lawndale. He lives with his mother in Hawthorne. His mother and other family members are in Yosemite. They said the search was called off for the night on Sunday, but it will resume Monday morning.