It is a small shrub with white flowers and green oval shaped leaves.

The small white flowers are up to 8 mm (0.31 in) wide with pale anthers.

[2][3][4] Tremandra diffusa was first formally described in 1824 by Augustin Pyramus de Candolle from an unpublished description by Robert Brown and de Candolle's description was published in Prodromus Systematis Naturalis Regni Vegetabilis.

[4][5] The specific epithet (diffusa) is derived from the Latin diffusus meaning "spread out", "extended" or "diffuse", usually referring to the habit.

[6] The species is found in the south-west corner of Western Australia growing on flatlands, outcrops and road verges in loam, sand and lateritic soil.