In the current context of global climate change, atmospheric carbon dioxide (CO₂) concentrations are continuously rising with potential influence on plant–herbivore interactions.The effect of elevated CO₂ (eCO₂) on feeding behavior of corn leaf aphid, Rhopalosiphum maidis (Fitch) on barley seedlings Hordeum vulgare L. was tracked using electrical penetration graph (EPG). The nutrient content of host plant and the developmental indexes of aphids under eCO₂ and ambient CO₂ (aCO₂) conditions were also investigated. Barley seedlings under eCO₂ concentration had lower contents of crude protein and amino acids. EPG analysis showed the plants cultivated under eCO₂ influenced the aphid feeding behavior, by prolonging the total pre-probation time of the aphids (wandering and locating the feeding site) and the ingestion of passive phloem sap. Moreover, fresh body weight, fecundity and intrinsic population growth rate of R. maidis was significantly decreased in eCO₂ in contrast to aCO₂ condition. Our findings suggested that changes in plant nutrition caused by eCO₂, mediated via the herbivore host could affect insect feeding behavior and population dynamics.