[1][2][3][4][5] It originates at Corriganville Park by the Santa Susana Pass, travels for 12 miles (19 km) through Simi Valley, leaves the city limits of Oak Park at the western end of Simi Valley, continues for seven miles in Moorpark where it merges with Arroyo Las Posas by Hitch Road.

[8] Arroyo Simi drains an area of 343 square miles in southern Ventura County.

[1] In its natural state, it is an ephemeral creek, which is only seasonally filled during winter time and periods of heavy rain.

Today it is for the most part a concrete lined water drain that flows year round.

It is home to fish species such as the brown bullhead, green sunfish, bluntnose minnow, and mosquitofish.