Synophromorpha Ashmead is a genus of cynipid inquilines associated with Diastrophus galls on Rubus bushes. All described species, except S. tobiasi which doubtfully belongs to the genus, are restricted to the Nearctic Region. Synophromorpha taketanii sp. n., a fifth species of this genus, is described from Japan. This is the first reliable record of the genus from the Palaearctic Region and reveals that Synophromorpha has a disjunct distribution. Adults of S. taketanii emerged from stem galls on Rubus palmatus. Study of Periclistus natalis and P. quinlani showed that Synophromorpha and Periclistus intergrade. It is considered preferable to retain these two as separate genera on the basis of their host associations.