The district is located at the base of the Santa Monica Mountains, bounded by the San Diego Freeway on the east, Wilshire Boulevard on the south, the Santa Monica city limits on the southwest, the border of Topanga State Park on the west and Mulholland Drive along the ridgeline of the mountains on the north.
Brentwood, like nearby Santa Monica, has a temperate climate influenced by marine breezes off the Pacific Ocean. Residents frequently wake to a "marine layer," a cover of clouds brought in at night which burns off by mid-morning.
The topography is generally split into two characters, broadly divided by Sunset Boulevard: the area north of Sunset is defined by ridges and canyons of the Santa Monica Mountains; south of Sunset the area is hilly. The southern district features underground springs which bubble up into a small creek along "the Gully" near the Brentwood Country Club, and in the "Indian Springs" portion of the University High School campus, formerly the site of a Native American Tongva village.