Castaic Lake State Recreation Area is a reservoir of the State Water Project. It is one of the Project's largest recreational lakes and the terminal of its west branch. The site includes 29 miles of shoreline. A major attraction is the 425-foot tall Castaic Dam.

Castaic Lake has two bodies of water. Lower lake is for non-power boating and canoeing. Swimming season on lower lake runs from mid-May to mid-September. Upper lake is for sailing, power boating, water and jet skiing, and fishing. The lake is stocked with bass, trout and catfish. Boat rentals and a tackle bait shop are available.

Other recreational activities include hiking, biking trails, picnic areas and playgrounds. Rental group picnic areas are available for up to 600 persons.