Perennials, 5-35 cm (taproots slender, caudices branched). Stems 1-4, erect, slender to stout, simple or sparsely branched, glabrate to tomentose and bristly-setose. Leaves basal and cauline; petiolate; basal blades lanceolate, 7-25 × 2-4 cm, margins deeply pinnately lobed (lobes lanceolate, dentate, teeth mucronate), apices acuminate, faces tomentulose (at least when young). Heads 1-9, borne singly or 2-9 in cymiform arrays. Calyculi of 8-10, lanceolate, tomentose and often setose bractlets 2-4 mm. Involucres cylindric, 11-21 × 5-10 mm. Phyllaries 8-18, (medially green) lanceolate, 10-16 mm, (bases keeled, margins yellowish, often scarious), apices acute, abaxial faces often densely, blackish or whitish tomentose or setose, sometimes glabrous, adaxial with fine (shiny) hairs. Florets 10-60; corollas yellow, 13-22 mm. Cypselae blackish or greenish, reddish, reddish brown, or yellowish, subcylindric to fusiform, 7-12 mm, apices tapered or beaked (beaks 1-3 mm), ribs 10 (strong to weak); pappi dusky white, 5-13 mm. 2n = 22, 33, 44, 55, 66, 88.

Crepis modocensis is recognized by its tomentose or coarsely bristly stems and petioles, rosettes of deeply pinnately lobed leaves, rather large heads with relatively many phyllaries, and blackish cypselae.