As global plastic production continues to grow, microplastics released from a massive quantity of plastic wastes have become a critical environmental concern. These microplastic particles are found in a wide range of living organisms in a diverse array of ecosystems. In this study, we investigated the biological effects of polystyrene nanoplastics (PSNPs) on development of the central nervous system using cultured neural stem cells (NSCs) and mice exposed to PSNPs during developmental stages. Our study demonstrates that maternal administration of PSNPs during gestation and lactating periods altered the functioning of NSCs, neural cell compositions, and brain histology in progeny. Similarly, our in vitro study also shows PSNP-induced molecular and functional defects in NSCs. Finally, we show that the abnormal brain development caused by exposure to high concentrations of PSNPs results in neurophysiological and cognitive deficits in a gender-specific manner. Our data demonstrate the possibility that exposure to high amounts of PSNPs may increase the risk of neurodevelopmental defects.