Argemone mexicana, Cipadessa baccifera, Clausena dentata, Dodonaea angustifolia and Melia dubia are medicinal plants predominantly present in India. The individual and synergistic effects of A. mexicana leaf powder with the other plants were investigated for their insecticidal property against Helicoverpa armigera. The different treatments differed significantly in their efficacy with 5 gm of A. mexicana + D. angustifolia and A. mexicana + M. dubia being the most effective in curtailing the pupation followed by 10 gm of A. mexicana alone. The pupal weight and length were low in the synergistic combination. Malformed moth emergence was 89% in 5 gm of A. mexicana + C. dentata. The adult life span was least in A. mexicana + C. baccifera. The fecundity and egg hatchability were also subsequently affected due to the impact on the first generation larvae.