For the first time eggs, larvae and pupae obtained by rearing are described for Astrapaeus, a monotypic West Palearctic rove beetle genus of a puzzling phylogenetic position within the mega-diverse tribe Staphylinini. Morphology of the immature stages of Astrapaeus ulmi is compared to that of other members of the tribe and discussed in a phylogenetic context. Contrary to conventional systematics and in accordance with recently developed phylogenetic hypotheses based on morphology of adults, larval morphology supports the non-Quediina affiliation of Astrapaeus. Eggs and pupae provided fewer characters with putative phylogenetic signal. Under laboratory conditions, a peculiar preference for isopod prey was observed for A. ulmi. However, this could not be evaluated in an evolutionary context because of the lack of data on the diet of this and related taxa in nature.