It is a small shrub, with linear leaves and mostly white flowers.

The flowers are borne singly in the leaf axils, corolla 8–10 mm (0.31–0.39 in) long, lobes more or less triangular shaped, 1.6–2.8 mm (0.063–0.110 in) long, 0.9–1.2 mm (0.035–0.047 in) wide, mostly white or occasionally mauve with spots purple or light brown and silky inside.

The green calyx are smooth or with sparse hairs on the outer surface and bracteoles 1–2 mm (0.039–0.079 in) long.

Flowering occurs mostly from July to December[2][3][4][5] Westringia longifolia was first formally described in 1810 by Robert Brown and the description was published in Prodromus florae Novae Hollandiae.

[8] Long-leaves westringia grows in gullies, near streams on sandy or loamy soils north of Mittagong, scattered throughout Sydney and the Central Tablelands.