The sighting was reported at about 4 p.m. in the hills above the Pillar Ridge Trailer Park in Moss Beach, according to the county's office of emergency services.
Mountain lions usually try to avoid contact with humans. Residents are advised not to approach mountain lions, and to try to appear large and make noise if one is nearby. The cats are most active at dawn, dusk and at night.
For more information about mountain lions, visit www.keepmewild.org.