The pollution of agricultural systems and plant health by heavy metals poses a major threat to human health. Excessive accumulation of cadmium, lead, arsenic, and mercury impairs the physiological function of plants, reduces crop yields, and pollutes the food chain. Chitosan nanoparticles (CNPs), as an environmentally friendly plant, might be an efficient approach to tackle heavy metal pollution. CNPs can bind large amounts of toxic metal ions, reduce bioavailability and mitigate oxidative harm to plants because of their enormous surface area, functional groups, and chelating capacity. The chapter showcases the processes involved in the reduction of heavy metal toxicity by CNPs, such as the increased activity of antioxidant enzymes, improved photosynthetic efficiency, membrane stability and the activity, and level of metal transporters. The use of CNPs is effective in plants exposed to heavy metal stress, resulting in improved plant growth, and biomass creation, as well as physiological stability. Moreover, CNPs may be constructed to provide key nutrients or signaling molecules, providing a multifunctional aspect of remediation and stimulation of growth. Despite this tremendous potential, issues of standardization of nanoparticle formulation, fate in soil–plant systems, and long-term effects on the soil environment are still unresolved. All in all, the idea of CNPs as a multifunctional, sustainable, and promising method of heavy metal stress in agriculture is gaining ground to serve environmental protection and clean crop production.