Abstract: Improving the efficiency of fertilizer use is an important way to reduce its use. Agricultural digitalization provides a new perspective for continuously improving fertilizer use efficiency. Based on panel data from 30 provinces (municipalities and autonomous regions, excluding Xizang Autonomous Region, Hong Kong, Macao, Taiwan) in China from 2012 to 2021, this study used a non-expected output SBM model with a global reference and entropy method to measure the efficiency of fertilizer use and the level of agricultural digitalization. After calculation, the average efficiency of fertilizer use was around 50%, and the average level of agricultural digitalization was 0.122. The level of agricultural digitalization was relatively weak, and more policy support was needed. This study used a panel Tobit model and a mediating effect model to empirically analyze the impact of agricultural digitalization on fertilizer-use efficiency and its path of action. The results demonstrated the rapid development of agricultural digitalization in China since 2019. However, there were obvious regional differences in the level of development, with the eastern region being higher than the national average and the middle and western regions being lower. The benchmark regression results showed that agricultural digitalization significantly improved fertilizer use efficiency at the 1% significant level, and the conclusion remained valid after the endogeneity treatment and robustness test. The mechanism test demonstrated that agricultural digitalization improved fertilizer use efficiency by expanding the scale of agricultural land operation, promoting the development of agricultural socialized services, and using green technologies. The heterogeneity analysis demonstrated that agricultural digitalization has a significant positive impact on fertilizer use efficiency in non-grain-producing areas and western regions, but none in grain producing areas, the eastern and central regions. Therefore, we should continue positively to improve fertilizer use efficiency through agricultural digitalization, promote the transformation of agriculture in rural areas, improve the platform of the land transfer market, promote the development of socialized agricultural services, strengthen the promotion and training of green technologies, provide impetus to improve the mediating role, strengthen supporting for agricultural digitalization development in the western region and explore suitable agricultural digitalization technologies according to local conditions.