The appearance of Phyllium gantungense "Rizal" varies significantly depending on the insect’s sex and developmental stage.
Nymphs: Newly hatched nymphs are dark brown or black with white highlights, measuring ~16mm in length and ~7–8mm in width. They strongly resemble large ants in appearance. Within several weeks of feeding, they transition to the leaf insect's characteristic green colouration.
Females: Adult females of Phyllium gantungense "Rizal" have an exquisite body shape. While flattened, they have less irregular bodies compared to other species, featuring a box-like form and uniquely shaped abdomen. They have enlarged forelegs and are almost exclusively green in colour with brownish-red variations on their body. Females reach ~90–100mm in length. They possess large, broad, non-functional forewings that cover almost the entire abdomen. Two short antennae, each measuring about 5mm in length, complete their appearance.
Males: Adult males of Phyllium gantungense "Rizal" are smaller, reaching sizes of ~55–60mm. Like the females, they are green in colour but possess fully developed wings enabling flight. Their antennae are notably longer than those of females, measuring about 50mm in length.