Abstract: Foliar fertilization is a popular strategy used to reduce fertilizer input and improve nitrogen use efficiency, crop yield, and quality. The effectiveness of foliar application and the efficient assimilation of urea by leaves are influenced by various factors, including foliar structure, environmental conditions, and carbon-nitrogen metabolism. However, most existing studies have focused on the impacts of foliar fertilizer application, with a comprehensive understanding of the mechanisms and regulation of foliar nutrient absorption and utilization still lacking. This knowledge gap limits further improvement of nitrogen-use efficiency and crop quality. In this review, we present a systematic summary of recent advancements in leaf anatomy structure, physiological and molecular mechanisms governing urea uptake and transport, as well as the identification of key genes involved and underlying mechanisms and regulatory networks of foliar urea uptake and metabolism. This review should help inform further research, potentially guiding strategies to promote sustainable agriculture, reduce fertilizer input, and enhance efficiency and food quality.