Oak Park is situated in southeastern Ventura County. It is bordered on the west by North Ranch (Thousand Oaks) and on the south by the LA County cities of Agoura Hills and Westlake Village. It borders the Santa Monica Mountains National Recreation Area to the east and north. Oak Park is the biggest unincorporated community in Ventura County. The location of Oak Park was originally part of Rancho Simi. Lindero Canyon Road follows the western border-line of the land grant.

The community is served by the Oak Park Unified School District (OPUSD), which has three elementary schools K-5, a middle school 6-8, Oak Park High School, Oak Park Independent School, and Oak View High School. Open space and parks in Oak Park are managed by the Rancho Simi Recreation and Park District. Oak Park borders the Santa Monica Mountains National Recreation Area. Trails are used for hiking, running, horseback riding, climbing, and mountain biking.