Department spokesman Steve Martarano said someone reported seeing a cougar about the size of a large dog perched in a tree in Eagle Rock.
The cat was also observed by an LAPD helicopter pilot orbiting the area.
If it is found, Martarano said the animal will be tranquilized and removed. He said it may be a young mountain lion looking for food in the hilly neighborhood.
Mountain lions occasionally venture into foothill communities in Southern California, where development has eaten away at their habitat.