It is native to the coastal mountain ranges and hillsides of southern California and Baja California, where it grows in local habitat in the canyons and slopes, such as coastal sage scrub and chaparral.

Lupinus longifolius is a bushy, erect shrub which can reach a maximum height around 1.5 meters.

The herbage is green or gray-green and coated in short, silvery hairs.

The inflorescence is long, narrow raceme of many flowers each between 1 and 2 centimeters in length.

The fruit is a dark-colored, hairy legume pod containing 6 to 8 seeds.