Aphelocoma californica, commonly known as the California scrub jay, is primarily found along the western coast of the United States. Its geographical distribution includes regions from southern Washington down through western Oregon to California and extends into the northern part of Baja California in Mexico.

California scrub jays inhabit a variety of environments characterized by Mediterranean climates. These areas typically experience wet, mild winters and dry, hot summers. The species is commonly found in oak woodlands, mixed evergreen forests, and chaparral habitats. They are also found in urban and suburban settings where suitable habitat is available.

Aphelocoma californica plays a key ecological role as both a seed disperser and a predator. They feed on a diverse diet that includes insects, small animals, seeds, fruits, and nuts, particularly acorns. This diet allows them to impact their ecosystem by controlling insect populations and aiding in the dispersal of certain plant species, especially oaks.