The genus Sciadiocoris gen. nov. is described to accommodate three new species of oncomerine true bugs from Papua New Guinea, Sciadiocoris constanti sp. nov., Sciadiocoris linnavuorii sp. nov. and Sciadiocoris raunoi sp. nov. Habitus as well as male and female genitalia are illustrated. The general aspect of the new genus is similar to that of Cumare Blöte, 1945, but the genitalia are strongly different. A revised key to genera of the subfamily Oncomerinae is given.