It is an open shrub with thin, square stems, simple, serrated leaves, and pink to mauve, four-petalled flowers.

The flowers on the edges of the cymes are borne on a thin, dark red pedicel 7–20 mm (0.28–0.79 in) long.

The description was published in the journal Vestnik Kralovske Ceske Spolecnosti Nauk, Trida Matematiko-Prirodevedecke.

[5] This boronia grows near swamps, along streams, along roads and in seasonally wet places between Busselton, Augusta, Nannup and Walpole.

[2][3] Boronia tenuior is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.