Abstract In plants, one of the most sophisticated defensive strategies against herbivores is producing toxic metabolites for protecting themselves. 2-Tridecanone, which has been identified as a plant-derived and herbivore-induced defensive substance of plants, plays a role in retarding the development and decreasing the survival rate of Lepidopteran larvae. In the present study, we comprehensively evaluated the overall toxic effects of 2-tridecanone on the oriental armyworm, Mythimna separata Walker, 1851 (Lepidoptera: Noctuidae), a notorious polyphagous pest. Our results revealed that 2-tridecanone at a sublethal concentration for the second-instar significantly delayed larval development, lowered the body weight of larvae and pupae, decreased the pupation and emergency rates, reduced the mating rate of adults, and impaired the fecundity of female moths. Notably, the fecundity and net reproductive rate (R0) of the F1 generation in the 2-tridecanone treatments were also reduced, indicating that the effects of 2-tridecanone are transgenerational in M. separata population. Our findings demonstrate the direct and long-term influence of 2-tridecanone on pests, and contribute the development of sustainable and eco-friendly pest management strategies.