It is an erect shrub with narrow oblong leaves and flowers arranged singly or in groups of up to three on a rachis up to 4 mm (0.16 in) long.

Persoonia flexifolia is an erect shrub with its young branchlets covered with whitish or greyish hairs.

The tepals are narrow oblong, 10–12 mm (0.39–0.47 in) long and glabrous on the outside with anthers that curve outwards near the tips.

[6][7] This geebung is only known from collections made at Lucky Bay and the Lort River in the Esperance Plains biogeographic region where it was growing in low heath.

[3][5] Persoonia flexifolia is classified as "Priority One" by the Government of Western Australia Department of Parks and Wildlife,[5] meaning that it is known from only one or a few locations which are potentially at risk.