Background and Objectives: Ooencyrtus egeria Huang and Noyes is an effective solitary egg parasitoid of Brachynema germari Kolenati and Acrosternum arabicum Wagner, the most common stink bugs of pistachios in Rafsanjan, Iran. Basic biological information on parasitoid and host interaction is essential for increased efficiency and successful biological control programs. Materials and Methods: In the present study, some important biological characteristics of O. egeria on two pistachio green stink bugs, A. arabicum and B. germari, were evaluated to define the best laboratory host for the mass rearing of this wasp. Results: The eggs of B. germari had better nutritional quality for O. egeria females, thus, having the highest parasitism rate compared to the eggs of A. arabicum. The number of female offspring that emerged from B. germari eggs was higher than that of A. arabicum,however, the highest survival rate and the lowest mortality rate were recorded for the A. arabicum. Conclusion: Although the laboratory results show that the survival rate is higher and the mortality rate is lower for A. arabicum, B. germari is a more suitable host for the rearing of O. egeria in laboratory conditions due to the higher parasitism rate and sex ratio. The present research findings could be used in pistachio orchards to provide necessary data enabling the best use of this egg parasitoid as a biocontrol agent.