Proterosceliopsis was erected by Ortega-Blanco et al. (2014) in their treatment of scelionid genera in Cretaceous amber from Álava, Spain. The generic description appears to have been based on specimens in which only the dorsal aspects of the mesosoma and metasoma were visible, as characters of the mesopleuron, metapleuron, lateral pronotum, and ventral metasoma were not mentioned. We here provide a comprehensive description of the genus that includes characters from throughout the body and we reinterpret some of the characters presented by Ortega-Blanco et al. (2014). Our analysis of Proterosceliopsis in the context of extant and fossil platygastroids places this group as a lineage well outside of the current families. We here designate Proterosceliopsis as the type genus of a new family, Proterosceliopsidae Talamas, Johnson, Shih & Ren, fam. nov., and describe five new species: Proterosceliopsis ambulata Talamas, Shih & Ren, sp. nov., P. nigon Talamas, Shih & Ren, sp. nov., P. plurima Talamas, Shih & Ren, sp. nov., P. torquata Talamas, Shih & Ren, sp. nov., and P. wingerathi Talamas, Shih & Ren, sp. nov. We provide a key to all presently known species in the genus. The oldest known specimen of Platygastridae s.s., in Burmese amber, is presented and compared to Proterosceliopsidae fam. nov.