The animal was spotted at about 2 a.m. behind a home in the 1200 block of Encina Drive, located near Mills Estate Park.
The mountain lion was seen on surveillance video and had jumped over a 6-foot fence to enter the yard, which contains a large koi pond. The animal was last seen heading east from the property.
County officials warn residents to avoid confrontations with mountain lions, especially if one is feeding or with offspring.
More information about mountain lions can be found online at www.keepmewild.org.