This chapter reviews chitosan-based nanoparticles for brain drug delivery, focusing on their ability to cross the blood-brain barrier (BBB) and improving treatment for neurological disorders. It covers chitosan nanotechnology, its properties, and fabrication methods. This chapter also discusses transport pathways, such as adsorptive-mediated transcytosis and receptor-mediated transport. It explores therapeutic uses in neurodegenerative diseases, cancer, and psychiatric disorders, emphasizing hybrid nanocarriers and gene delivery systems. Challenges in manufacturing and regulation are highlighted, along with future trends in personalized medicine, neural stem cell-based delivery systems, and CRISPR-Cas9 technology.