The leaves of Mitragyna parvifolia grow opposite on the stem.
The leaf is simple, bright green-coloured above and paler beneath. The leaf is glabrous on both sides (some minute hairs on the midrib beneath).
The leaves have a 1-1.5 cm long petiole.
The leaf of Mitragyna parvifolia is 7-11 cm long and 4-6 cm wide. The shape of the blade is ovate to oblong, the apex is obtuse, the base is rounded and the margins are entire.
The venation of the leaf is reticulate with a prominent midrib.