Glendora police responded to a call about a bobcat around East Leadora Avenue just after 6 a.m.
After responding, officers determined it was a mountain lion weighing about 100 pounds.
Officers tried to get the big cat back up into the hills, but he kept roaming, eventually jumping into a backyard and then climbing up a tree.
The Department of Fish and Wildlife finally tranquilized the cat and relocated him back into the hills.