Though both its common and scientific names refer to San Diego, Diaulula sandiegensis occurs along the coast of the northeastern Pacific, from Alaska to Puerto Penasco, Mexico.

[3] Their mantle has a velvety appearance, created by minute spiculate papillae (caryophillidia); these sensory nodules are typical of dorid nudibranchs.

While mating, individuals wrestle for dominance, attempting to penetrate and impregnate the other by darting their penises into their body wall.

[3] After undergoing metamorphosis, Diaulula sandiegensis will spend its life in the benthic zone, using specially developed pedal ganglia in their foot to assist in movement like many other bottom-dwelling nudibranchs.

These ganglia work by producing peptides which elicit an increase in the rate at which the cilia on the underside of the foot beat, resulting in crawling.