Stems (25-)40-80(-180) cm; base usually reddish, pubescent. Leaves cauline and basal; basal leaves 0-5 at anthesis; cauline leaves 2-8 at anthesis; petiole 0.5-8 cm, petioles of proximal leaves long-pubescent. Leaf blade pentagonal, 1.5-5 × 2.5-8 cm, long-pubescent, especially abaxially; ultimate lobes 0-18, width 4-20 mm (basal), 2-9 mm (cauline). Inflorescences (9-)15-40(-160)-flowered, dense to open; pedicel 0.3-2.5(-6) cm, puberulent; bracteoles 1-5(-8) mm from flowers, green, sometimes white-margined, linear-lanceolate, 2-6(-8) mm, puberulent. Flowers: sepals violet to white, ± puberulent, lateral sepals spreading to forward pointing, 7-10(-13) × 3-6(-8) mm, spurs gently upcurved, ascending 0-30° above horizontal, (6-)9-13(-16) mm; lower petal blades elevated, ± exposing stamens, 3-7 mm, cleft 1-2(-4) mm; hairs centered, densest on inner lobes near base of cleft, white. Fruits 8-20 mm, 2.2-4 times longer than wide, glabrous. Seeds echinate, appearing fuzzy to naked eye; seed coat cells with margins straight, surfaces sparsely pustulate.

Although Delphinium hansenii has often been confused with D . hesperium , seeds will instantly allow identification. Seeds of Delphinium hansenii are, as far as known, unique, bearing numerous, elongate, prismlike raised structures (extensions of single cells or small groups of cells) over the entire seed coat. If seeds are absent, larger flowers, more open inflorescences (except in D . hesperium subsp. cuyamacae ), and general absence of pubescence of long hairs in D . hesperium are apparent upon comparison of the two species. Separating D . hansenii from D . variegatum may also be difficult. Again, seeds leave no doubt. In addition, smaller flowers and greater number of flowers per plant of D . hansenii should serve to distinguish D . hansenii from D . variegatum . White-flowered D . hansenii has been confused with D . gypsophilum and with D . hesperium subsp. pallescens . Other than seeds, pubescence of long hairs and smaller flowers present in D . hansenii and absent in the others will distinguish them.