The simple, usually opposite leaves of Jamesbrittenia breviflora are oval in outline, the margins shallowly scalloped or sometimes entire. The leaves grow stalked with bluntly pointed to rounded tips and square to lobed bases. The leaf midribs and ascending lateral veins that split near the margins are all sunken on the upper surfaces, giving the blades a quilted appearance. Glandular hairs are also present on the leaves. The leaves are up to 35 mm long and well narrower than that (Manning, 2009; Pooley, 1998; iNaturalist; https://pza.sanbi.org).