Rhombodera kirbyi is known for its impressive size and distinctive appearance. The adults of this species can grow to be quite large, with females reaching lengths of around 4 to 5 inches (10 to 12.5 cm) or even more. The coloration can vary, but it often includes shades of brown, green, and sometimes pink.
One of the notable features of Rhombodera kirbyi is the shield-like extension of the thorax, which gives the mantis its common name. This shield, combined with its overall body shape, provides it with a unique and somewhat angular appearance.