It is an upright, annual herb with stems branching from the base and yellow or white flowers and is endemic to Western Australia.

Hyalosperma simplex is an upright, annual herb up to 10–15 cm (3.9–5.9 in) high with simple stems or sparingly branched from the base with a cottony appearance.

The leaves are arranged opposite, rounded on one side, flat on the other, about 10 mm (0.39 in) long, pointed, occasional cottony hairs to smooth.

The single yellow or white flower heads are at the end of branches and up to 2 cm (0.79 in) in diameter.

[2][5] The specific epithet (simplex) means "simple, not divided" referring to the stems.