Following the recent revision of Microbrotula (Schwarzhans Nielsen, 2011), an additional nine specimens of the viviparous genus Microbrotula (Teleostei: Bythitidae), all caught in the Cenderawasih Bay, Irian Jaya, New Guinea, Indonesia, were made available to us. These specimens represent a new species described here as M. geraldalleni. It belongs to the group of species with 6 caudal and 14 pectoral fin rays and is closest to M. greenfieldi, differing in the higher dorsal and anal fin ray counts (68-73 and 61-65 vs. 62-70 and 58-61, respectively), the presence of 3 posterior mandibular pores (vs. none), 2-3 preopercular pores (vs. none), a connected squamation over the head including cheek, opercle and occiput (vs. 3 separated scale patches) and with a unique scale-less triangular window just above the opercle. Microbrotula geraldalleni may be endemic to the Cenderawasih Bay.