California Scrub-Jays eat mostly insects and fruit during spring and summer. They switch to nuts and seeds during fall and winter, especially acorns. They also eat small animals such as lizards and nestling birds, sometimes shadowing adult birds to find their nests.

The generic name Aphelocoma derives from Latinized Ancient Greek apheles- (from ἀφελής-) "simple" + Latin coma (from Greek kome κόμη) "hair", in reference to the lack of striped or banded feathers in this genus, compared to other jays. californica, Latin: "from California".