Seaweeds are widely occurring natural resources in marine ecosystem which possess various bioactive compounds which were reported to active against many insects of crops. The bio-efficacy of aqueous, solvent and fortified brown algal seaweed extracts of Turbinaria ornata at different concentrations (2, 4, 6, 8, 10 and 20%) along with standard check Neem leaf extract (NLE 3%) were tested (free choice test) against Rice leaf folder Cnaphalocrosis medinalis Guenee (leaf dip method) in laboratory conditions in Department of Entomology, Faculty of Agriculture, Annamalai University during 2021-2022 under Completely Randomized Design with three replications per treatment. Treated leaves after shade drying were fed to the test insect and based on their feeding and response data on larval mortality, pupation, pupal malformation and adult emergence was recorded and the data were analyzed statistically and presented. Compared to aqueous and solvent extracts, fortified seaweed solvent extracts with Neem leaf extract (3%) showed higher level of larvicidal action in which T. ornata (20%) + Neem leaf extract 3% recorded the highest larval mortality (56.66%), lowest pupation (43.33%), highest pupal malformation (20.00%) and the lowest adult emergence (26.66%) wherein the pupa to adult conversation ratio of 1:0.67 was lower when compared to standard check.