Agriculture, as a cornerstone of global food security, faces the intricate challenge of feeding a growing population while mitigating its environmental footprint. The expanding global population and food demands have led to an enormous increase in agro-industrial operations and products with a concomitant increase in non-consumable biomass—agro-industrial wastes. These wastes are largely left untreated resulting in environmental degradation and economic losses. Owing to their biochemical heterogeneity and presence of vital bioactive compounds like carbohydrates, proteins, and minerals, these can be used as feedstock for biorefinery for generation of a diversified variety of products including composts, organic fertilizers, and biochar, to name a few. With the advent of new techniques, the valorization of agro-industrial wastes as environment-friendly and sustainable tools for addressing the problems about conventional agricultural practices has grown tremendously. In recent decades, green nanotechnology has emerged as an acceptable approach for utilizing agro-industrial wastes to synthesize nanomaterials with excellent surface properties and biocompatibility which include, but are not limited to, nanoparticles and nanocomposites. This chapter focuses on examining and characterizing agro-industrial wastes as potential resources for generating cost-effective value-added nanomaterials, along with nano-management of agro-waste to improve the agricultural output. Furthermore, an assemblage of the approaches adopted for synthesis of various nanoparticles, along with the possible applications is put forth.