Bornetia secundiflora is dark red in colour, firm and rigid when fresh. The thallus is 5-20 cm high when erect, fan-shaped with blunt tips (apices), much branched and tufted, with branches often curved over. The plant has a jelly-like texture. Branches are sparse at the base becoming more dense towards the apices.

Bornetia secundiflora shows little variation other than in overall size. The species is one of the most easily recognisable member of the Ceramiaceae. The only confusion possible is with Griffithsia corallinoides, from which it differs by the rigid rather than flaccid texture and the cylindrical rather than bead-like apical cells.