Trees , evergreen, to 25 m. Bark gray to dark brown or black, ridges broad, rounded. Twigs brown to red-brown, 1.5-3 mm diam., with scattered pubescence or uniformly pubescent. Terminal buds light chestnut brown, ovoid, occasionally subconic, 3-6(-7) mm, glabrous except for cilia along scale margins. Leaves: petiole 4-15(-18) mm, sparsely to densely pubescent. Leaf blade broadly elliptic to ovate or oblong, 15-75 × 10-40 mm, base rounded or cordate, margins entire or spinose, with up to 24 awns, apex blunt to attenuate; surfaces abaxially glabrous or with small axillary tufts of tomentum, veins raised, adaxially distinctly convex, rugose, glabrous, occasionally densely uniformly pubescent. Acorns annual; cup turbinate to cup- or bowl-shaped, rarely saucer-shaped, 9-13 mm high × 9-15 mm wide, covering 1/4-1/3(-1/2) nut, outer surface glabrous to sparsely puberulent, inner surface pubescent on innermost 1/3 to uniformly pubescent, scales acute, tips loose; nut ovoid to oblong or conic, 15-35 × 10-15 mm, glabrous, scar diam. 3.5-8 mm. 2 n = 24. Flowering early to mid spring. Moderately dry sites; to 1400 m; Calif.; Mexico (Baja California). Quercus agrifolia is found in the Coast Ranges from Sonoma County, California, south to Baja California. Plants with densely pubescent leaves, especially abaxially, have been treated as Q . agrifolia var. oxyadenia . This species reportedly hybridizes with Quercus kelloggii and Q . wislizenii .
The Mahuna used Quercus agrifolia medicinally to heal the bleeding navel of a newborn (D. E. Moerman 1986).