Arroyo Seco[1] is a 6.9-mile-long (11.1 km)[2] tributary stream to Schell Creek in southern Sonoma County, California, United States.

Arroyo Seco Creek drains a portion of the western slopes of the southern Mayacamas Mountains.

Its 11.4-square-mile (30 km2) watershed,[3] along with the entire Mayacamas mountain block, was formed in the Miocene era by volcanic action and with tectonic uplift about 12 million years ago.

Soils of the immediate streambed and its vicinity are classified as the riverwash series, recent deposition of sands and gravels.

[4] Arroyo Seco Creek springs near the Napa County line about 4 mi (6 km) northeast of Sonoma, California.