Nanosensors are essential for advancing our understanding of neural health by providing high-resolution, real-time monitoring of neural activity and biomarkers. Nanoparticles like carbon-based structures, quantum dots, and gold nanoparticles-based sensors offer unique capabilities to monitor protease activities, ion concentrations, and other biomolecules in neural cells. In addition to monitoring, nanofluidic mechanisms and biosensors enable precise control of chemical release for neurotransmission mimicking and neurostimulation. Detection of neuronal signals and facilitates the study of neural networks in vitro can be enhanced by integrating nanosensors with multi-electrode arrays and magnetic sensor arrays. Neural health research can be revolutionized and paved the way for innovative diagnostic and therapeutic strategies in neurology and neuro-engineering by integrating with nanosensors. Nanosensors also have potential in brain–machine interfaces (BMIs), application including enhanced neuroprosthetics, facilitating brain–computer communication, and advancing our understanding of brain function and nanotechnology combined with brain–machine interfaces (BMIs), to create more efficient and reliable interfaces for decoding and encoding neural information. This chapter explores the current state and significance of nanosensors in neural health research and brain–machine interfaces (BMIs), focusing on their ability to detect and measure various physiological–pathological changes in neuronal cells and enabling high-resolution monitoring and modulation of neural activity.