Two new species of Quadrisegmentum (Phtisicidae: Amphipoda: Crustacea) are described from the Central Indo-Pacific. The new species Quadrisegmentum atauro sp. nov., is described from the Wetar Basin, Timor-Leste in the Lesser Sunda Region of the Western Coral Triangle. The new species name Q. yirrgay sp. nov., is established for material from Ashmore Reef in Queensland and Papua New Guinea originally reported under the name Q. triangulum Hirayama, 1998 (Guerra-García 2003, 2006; Guerra-García & Lowry 2009). Study of the type material of Quadrisegmentum triangulum described from Ashmore Reef in the Timor Sea, Western Australia confirms the absence of projections on pereonite 2, which prompted reassessment of subsequent identifications. Records of Q. triangulum are now limited to the type locality only. An updated key to the four known species of Quadrisegmentum is provided.