The Fall army worm, Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae) is a polyphagous pest native to the tropical and subtropical regions of America. In Asia, S. frugiperda was first detected in the southern state of Karnataka, India. Since the S. frugiperda occurrence, limited information is available on its biology in different host plants. Host plants play a crucial role in the life cycle of insect and may be used for pest management strategies. Therefore, the study aimed to investigate the reproductive, developmental and population growth parameters of S. frugiperda on castor and maize under laboratory conditions. According to the findings, significant variations were observed in all the reproductive parameters on both the host plants. The egg, larval, pupal duration and adult longevity of S. frugiperda significantly prolonged on castor as compared to maize. Minimum and maximum survival of S. frugiperda were noticed in castor and maize. Both the tested plants, castor had lower values of population growth parameters (net reproductive rate R0, intrinsic rate of increase Rm and finite rate of increase λ) and longer generation time Tc than that of maize. This research suggested that castor can contribute to the development and spread of this invasive pest in the absence of its regular host (maize).