Two zoeal and one megalopal stages of Petrolisthes unilobatus Henderson, 1888, are described and illustrated on the basis of laboratory-reared material. Petrolisthes unilobatus is easily distinguished from other species of Petrolisthes by the absence of setules (first zoea) or plumose setae (second zoea) on the dorsal surface of the second and third segments of the second maxilliped endopod. Zoeal characters of this species most closely agree with those of Group 1 identified by Osawa (1995), but differ from this group by having only a single short plumose seta on the posteromedian margin of the telson in second zoea. We provide a modified table of Osawa's larval groups and propose an additional larval group, Group 7, for P. unilobatus.