The stream begins at Mount Gleason, , in the western San Gabriel Mountains of the Angeles National Forest. The upper reaches, sometimes known as Pacoima Creek, flow through Pacoima Canyon as a rapid mountain stream. It then reaches the Pacoima Dam Reservoir in the western San Gabriel Mountains of the Angeles National Forest and proceeds south in a free-flowing stream alongside Pacoima Trail Road. Below the dam, it is generally known as the Pacoima Wash. From there, it joins several other unnamed streams that drain the nearby mountains, collecting at Lopez Dam. South of that dam, Pacoima Wash is encased in a concrete flood control channel, and travels south from Kagel Canyon in Sylmar though San Fernando, Pacoima, Mission Hills, Panorama City, and Van Nuys.