The nontarget effects of the plant growth regulator indol-3-acetic acid (IAA) on parasitoid development and reproduction were examined using the endoparasitoid Apanteles galleriae Wilkinson (Hymenoptera: Braconidae). The effects of IAA were assessed by rearing A. galleriae on hosts fed different doses of the growth regulator and then measuring a range of life history traits such as immature developmental time, adult longevity, body size, fecundity, and sex ratios in F₁ and F₂ generations. Wasp development from egg to adult took 27–47 d. However, adult emergence of parasitoids reared on hosts exposed to IAA doses required 14–24 d longer than controls to complete development at doses >200 ppm. Longevity of IAA-treated adult wasps was lower than that of controls at any dose. For example, at IAA doses >200 ppm, the life span of both male and female adult wasps decreased >50% compared with parasitoids that developed inside IAA-free hosts. Adult length also decreased at 500 and 1,000 ppm with respect to the control and lesser dosages. The total number of progeny decreased >50% and female sex ratio increased at doses >200 ppm compared with controls. Our results showed that the developmental biology of parasitoids exposed indirectly to IAA might be affected by high doses.