Crassula sarcocaulis is a small, evergreen, succulent sub-shrub, 250–400 mm high. The plants are tree-like in form, with a single main stem and a well-branched crown. On older specimens the bark is flaky or peeling. Leaves are flat and narrow, awl-shaped, up to 12 mm long, fleshy, light green. Clusters of small white to pinkish flowers are borne at the tips of the branches, and smell like honey or black currant jam. The individual flowers are cup-shaped, 3–5 mm long. Flowering time is late summer to autumn to winter (January to June).

Crassula sarcocaulis has two recognised subspecies: subsp. sarcocaulis and subsp. rupicola Toelken. The subsp. sarcocaulis has an upright habit with moderate branching and main branches up to 10 mm in diameter. Its leaves are elliptic, broadest at the middle, 5–30 mm long and 2–8 mm broad. It It flowers in autumn and winter (April–June). The subspecies rupicola is upright and spreading and much branched, forming dense shrubs with main branches up to 50 mm in diameter. The leaves are linear to lance-shaped and broadest towards the base, 8–20 mm long and up to 1.5 mm broad. It flowers in late summer to autumn (January–April).