The optimal use of egg parasitoids in crop protection requires an accurate knowledge of their biology. Parasitoid females and host egg ages is often regarded as two key elements in determining host acceptance and parasitoid capacity to exploit host eggs. Ooencyrtus egeria has recently been reported one of the egg parasitoids of Pistachio green stink bug, Acrosternum arabicum. Therefore, in the current work, the effects of host egg age and parasitoid on biological parameter of O. egeria were avaluated in conditions laboratory (27 ± 1 °C, 60 ± 5 % RH and 16 : 8 [ L:D ] h) using choice and no-choice tests. Host egg age tested were 24, 48, 72 and 96 -hour-old and the ages of parasitoid were 2 and 6-day-old .Results showed that the egg parasitoid preferred to parasitized 24-hour-old eggs rather than other eggs in choice assays. No statistically significant differences among the 24, 48, 72 and 96-hour-old age classes were observed in the no. parasitized host eggs in 2 and 6-day-old parasitoids in nochoice assays. In contrast, development time was longer in older host eggs, and females were smaller than those that developed in younger host eggs.The age of parasitoid females has an effect on parasitism rate, as 2-day-old females parasitized fewer eggs than 6-day-old females.This study demonstrated that both the aging of parasitoids and host eggs play a important role in the development of parasitoid offspring. The important of these results in the context of biological control programs involving Ooencyrtus parasitoids is discussed.