Investigations were carried out to evaluate the insecticidal potential of abrown algal seaweed Padina gymnospora on the leaf eating caterpillar, Spodoptera litura (Fabricius). In the Department of Entomology, Faculty of Agriculture, Annamalai University, India during 2019 - 2020. The seaweed solvent extracts (methanol, acetone and hexane) were screened against homogenous population of S. litura (third instar larva) using contaminated food bio-assay technique with the following concentrations 0.1, 1, 3, 5, 7, 10 and 20 per cent. The highest larvicidal activity (100%) was observed after 72 hours of treatment at the maximum concentration (20%) and the least larval mortality were observed in 0.1 per cent concentration of acetone extract (13.33%). Padina gymnospora at higher concentration levels influenced cent per cent larval mortality wherein none of the treated larvae have not transformed into pupa whereas the larva treated with hexane extract demonstrated insect growth regulator activity viz., pupal malformations whereas the adult emergence rate was lower in acetone extract as compared to hexane extract in the meantime cent per cent adult emergence was noticed in respective solvent and untreated control treatments. The observed larval: adult conversion ratio demonstrated that the methanol extract was superior than the acetone and hexane extracts.