The small, unisexual flowers of Euphorbia rhombifolia grow from nodes or axils of the upper stems. They are pale yellowish, sometimes tinged reddish-brown. In shape they appear saucer-shaped to cup-shaped, the male or female part protruding in the centre.

Flowering usually happens from spring to summer. These were seen in August (Shearing and Van Heerden, 2008; Gledhill, 1981; iNaturalist).