The cat was spotted by a resident in the 200 block of West Floresta Way shortly after 11 a.m., according to sheriff's Sgt. Gary Brown.
Brown said no physical evidence of the mountain lion was located, but a sheriff's deputy spoke with the resident and felt comfortable the resident had spotted the cat.
The area has lots of open space and mountain lion sightings are not uncommon, Brown said.
Anyone who sees the mountain lion is asked to call the sheriff's office at (650) 363-4915.