Herbivory is observed in different forms, one of these forms leading to gall production. Among gall–inducing insects, oak gall wasps (Hymenoptera: Cynipidae) are found on the oak trees producing galls on certain parts of the host. In this survey, oak gall wasps were collected from oak forests in West Azerbaijan in spring (2010). The occurred galls on oak trees (in spring) were collected from such locations as Ghabre-hosein, Mirabad, Vavan, Shalmash, Rabat and Dar-ghabr (a number of 40 trees in each site). In each tree, as a unit of sampling, all the occurred galls on 4 branches (each branch of 40 cm length, and each in any of the 4 geographical directions) were counted. Species richness was evaluated through Rarefaction and Jackknife methods and four similarity indexes calculated. During the survey, 7 oak gall wasp species (sexual generation) were indentified on oaks (Quercus infectoria, Q. brantii and Q. libani) in West Azerbaijan. Most of the galls occurred on Q. brantii. All collected oak gall wasps belonged to 3 genera, namely: Andricus, Chilaspis and Biorhiza. The highest number of expected species’ richness as determined through Rarefaction and Jackknife methods was estimated at 4.68 and 5.2 species respectively, in Mirabad region. The highest similarity indexes of Morisita, Horn, Renkonen and Sorensen were recorded between Ghabre-hosein and Mirabad in the sexual generation of oak gall wasp species. Difference in the local distribution of oak species (Quercus sp.) and subspecies shall be considered as one main factor involved in species diversity, and as well in the oak gall wasp species’ distribution in different locations under study.