The family Peradeniidae (Hymenoptera: Proctotrupoidea) is represented by two rare extant species from southeastern Australia (Australian Capital Territory, Victoria, Tasmania). A new species, Peradenia galerita sp. n., is described from Eocene Baltic amber. The fossil species is very similar to the living Perndenia, but has the short metasomatic petiole typical of most Proctotrupoidea. The subfamily classification of Heloridae proposed by Rasnitsyn and the status of Peradeniidae are briefly reviewed. The subfamily Mesohelorinae Rasnitsyn, 1990 is a junior synonym of Protohelorinae Rasnitsyn, 1980 (syn. n.).