Investigation of the antioxidant and oxidative effects of dietary indole-3-acetic acid (IAA), a plant growth regulator, on pest Galleria mellonella L. (Lepidoptera: Pyralidae) and its endoparasitoid Pimpla turionellae (L.) (Hymenoptera: Ichneumonidae) was aimed in this study. Different doses of dietary IAA (50-10,000 ppm) caused an increase in lipid peroxidation in the hemolymph of the host, G. mellonella (L.) and its endoparasitoid P. turionellae (L.). When compared to the control, higher doses of dietary IAA decreased CAT, SOD and GST enzymes' activities in G. mellonella. At higher IAA doses, the activity of SOD enzyme in the hemolymph of P. turionellae significantly decreased while CAT enzyme activity showed no significant change when compared to the control. Additionally, GST activity in the endoparasitoid larval hemolymph significantly increased at 500 and 1000 ppm IAA doses. These findings indicate that incorporating IAA in the diet of model host G. mellonella larvae leads to oxidative stress and, also negatively affects the survivability of both the host and its endoparasitoid.