A new crangonid genus, Placopsicrangon, is established for an unusual new species, P. formosa, which is described on the basis of material from off Taiwan in the northwestern Pacific, at the abyssal depths of 4412-4824 m. This new genus has a large and reflective plate-like eye that is unknown in decapod crustaceans before but similar to the eyes of the deep-sea grideye fish of the genus Ipnops Günther, 1878. The new genus is also unique within Crangonidae by having a laterally compressed rostrum with dentate dorsal margin, and the presence of a transverse row of sharp teeth adjacent to the posteroventral margin of the sixth pleonal sternite. Placopsicrangon appears closest to Sabinea in the general pattern of the carination on the carapace and pleon, and the substantially reduced non-chelate second pereiopod. This new taxon is the sixth representative of Crangonidae inhabiting the abyssal zone.