Maize is one of the most important cereal crops and is called ‘the queen of cereals’ because of its high yielding potential than other cereals. Fall armyworm, Spodoptera frugiperda is one of the serious invasive pests found to cause higher yield loss and extensive damage on maize. Considering the ecological and environmental consequences, biological control of insect pests is gaining importance as an alternative to insecticides. However, the success of any biological control programme depends on the appropriate parasitoid: host ratio and the biological stage of the pest susceptible to parasitoid. To fortify the above facts, the present study was aimed to determine the parasitic potential of B. brevicornis on S. frugiperda through free and no choice tests. This study indicated highest parasitization at the parasitoid: host ratio of 5:1 with 68.60 and 64.95 per cent parasitization on the VI instar followed by V instar (57.75 and 56.95 %), IV instar (48.80 and 46.60 %) and III instar (32.40 and 30.67 %) respectively under free and no choice conditions, respectively. Among the parasitoid host ratios tested 5: 1 was found to be the best indicating that the parasitic potential of B. brevicornis was directly proportional to the parasitoid densities. Biological parameters of B. brevicornis studied on different S. frugiperda instars recorded highest number of eggs (32.00), grub (30.75), cocoon (29.75) and adults (28.00) on sixth instar larva of S. frugiperda followed by fifth instar larva of S. frugiperda. The results revealed that the larval size was directly proportional to the progeny development of B. brevicornis. The egg, grub and cocoon period of B. brevicornis on S. frugiperda ranged from 24.20 to 26.20 h, 72.26 to 73.20 h, 96.20 to 98.20 h, respectively. The total life cycle was completed in 192.66 to 195.80 h in all instars and was found to be on par with all the instars studied. The longevity of adults emerged from different instars were found to be on par with each other and it ranged from 362.0 to 362.8 h.