This chapter explores recent trends in developing and applying nano-fertilizers, emphasizing their potential to enhance nutrient use efficiency, reduce environmental impact, and promote crop yield and soil health. The nano-fertilizers addressed included polymeric nanomaterials for nutrient-encapsulation and efficient delivery, and green-synthesized nanostructures to improve plant growth and physiological/biochemical plant functions. Furthermore, we compiled novel evidence highlighting the mechanisms of action of the presented nanomaterials, focusing on their capacity to orchestrate molecular events such as enzymatic and non-enzymatic reactions. This chapter also considered the challenges associated with the regulatory hurdles, toxicology, and public perception of nano-fertilizers. The role of nanotechnology in precision agriculture was critically analyzed, and how nano-fertilizers can be integrated into smart farming practices to optimize nutrient delivery and minimize waste. By exploring recent research findings and industry advancements, this chapter provided a comprehensive overview of the nano-fertilizers state of the art and their potential to transform sustainable agriculture. Given the experience of our research group working with nanotechnology and soil systems, future directions regarding research and rational development of nano-fertilizers are included.