Brachychiton rupestris grows as a succulent tree reaching 10–20 metres though plants in cultivation are usually shorter. The thick trunk is 5–15 metres tall, with a 1–3.5 metres diameter at breast height. It has dark grey bark and is marked by shallow tessellation and deeper fissures. Smaller branches are light green or grey, as are the trunks of immature trees.
Like those of all members of the genus, the leaves are alternately arranged along the stems. Trees in their native habitat are typically leafless between September and December.