Brown marmorated stink bug, Halyomorpha halys Stål, is an invasive species of Asian origin that is an important agricultural pest in the eastern United States. Sentinel egg masses are tools used to assess the impact of natural enemies on H. halys populations. To determine the effect of host egg age and storage conditions on their susceptibility to parasitism, H. halys eggs were stored at different temperatures for different lengths of time and then exposed to Anastatus reduvii (Howard), a native natural enemy of H. halys occurring in eastern North America. For eggs stored at 15, 20, and 25°C and then exposed to A. reduvii, the number of host eggs from which parasitoid offspring emerged declined with age of eggs. Control eggs (exposed to parasitoids without being stored) and those eggs stored for only 5.5 degree-days (DD) (=0.5 days) at 25°C yielded the highest percentage of parasitoids at 88.2 and 88.3%, respectively. For eggs stored at 20 and 25°C for 7.3 DD to about 36 DD, offspring emerged from about 58 to 73% of eggs, and total parasitism (emerged + unemerged parasitoids) ranged from about 70 to 80%. Parasitoid emergence was significantly lower for host eggs stored at 15°C for comparable times at 20 and 25°C. Stink bugs nymphs hatched from <0.6% of all eggs. Parasitoid-induced host egg abortion was an important component of egg mortality caused by A. reduvii, with underdeveloped stink bug nymphs, undifferentiated cell contents, and parasitoid host feeding occurring across all storage treatments.