Abstract: Background and Objective: In recent years, the increasing information on ill effects of artificial prepared chemicals and synthetic insecticides on plants health has alarmed researchers to seek some alternative ways, which are eco-friendly. The objective of this study was to identify the best medicinal plants seed extracts which can inhibit the growth of Trichoplusia ni and Pieris brassicae (lepidoptera) larvae. Materials and Methods: The insecticidal activity experiments were evaluated on two lepidoptera larvae species (Trichoplusia ni and Pieris brassicae ) by using four potential medicinal plants seed aqueous extracts (Latana camara, Sapindus trifoliatus, Solanum trilobatum and Ceiba pentandra) at 25-100 mg kg–1 concentrations. The data were analyzed using population standard deviation, calculated with online trial version (SPSS-IBM) product. Results: The medicinal plant seed aqueous extracts of Sapindus trifoliatus and Solanum trilobatum species showed rich amounts of phytochemicals like alkaloids, flavonoids and saponins showed best competence in controlling the insect larvae and caused delay in pupation at 100 mg kg–1 concentrations. Conclusion: The medicinal plant seed aqueous extract of Sapindus trifoliatus and Solanum trilobatum showed equal inhibition when compared to rosemary Oil. These plants species are suggesting its role as best bio-insecticides in the management of lepidoptera larvae pests.