The simple, opposite leaves of Justicia flava grow on short stalks spaced up the stems. They are ovate in shape with entire margins, rounded at the base and tapering to tips that are narrowly rounded or slightly, obtusely pointed.

The lower leaf surfaces are finely hairy, the upper ones about hairless. Leaf dimensions are 12 mm to 120 mm, by 4 mm to 46 mm (Pooley, 1998; Germishuizen and Fabian, 1982; Leistner, (Ed.), 2000; iSpot).