Abstract: Micronutrients are essential to the healthy growth of crops. Insufficient supply of these nutrients can hinder global agricultural productivity, compromise crop quality, and even pose potential risks to human health. Traditional micronutrient fertilizers, such as those containing iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn), are prone to fixation in soil, while boron (B) and chlorine (Cl) are easily leached. These issues lead to low nutrient utilization rates and considerable environmental risks. However, the emergence of nanotechnology offers a novel solution to these long-standing challenges. Nano-micronutrient fertilizers exhibit unique physicochemical properties, including the quantum size effect, high specific surface area, and enhanced reactivity. These characteristics endow them with great potential to improve nutrient utilization efficiency, promote crop growth, enhance stress tolerance, and elevate crop quality. This paper systematically reviews the latest research progress in nano-micronutrient fertilizers, elaborating on their main categories and preparation techniques. It also explores the underlying mechanisms of nutrient absorption, transport, and metabolism in crops. Furthermore, the paper comprehensively evaluates their practical applications in agricultural production, with a particular focus on their impacts on crop yield and quality. Finally, it forecasts the key challenges and future development directions in this field, aiming to provide valuable references for the scientific research, efficient application, and risk management of nano-fertilizers.