It has broadly linear, coarsely serrated, sharply pointed leaves, pale yellow flowers in heads of about sixty, and oblong to egg-shaped follicles.

Banksia trifontinalis is an openly branched shrub that typically grows to a height of 2 m (6 ft 7 in) but does not form a lignotuber.

Flowering occurs from August to September and the fruit is a sparsely hairy, oblong to egg-shaped follicle 6–9 mm (0.24–0.35 in) long.

[7][8] Banksia trifontinalis occurs only in a few populations in the vicinity of Arrino and Three Springs in the Geraldton Sandplains biogeographic region.

[2][3] This banksia is classified as "Priority Three" by the Government of Western Australia Department of Parks and Wildlife[3] meaning that it is poorly known and known from only a few locations but is not under imminent threat.