Bridging the “last mile” of promoting and applying new agricultural technologies faces deep-rooted challenges such as mismatches between supply and demand, weak promotion capabilities, and low willingness of farmers to adopt these technologies. To provide insights and references for improving China’s agricultural technology promotion system, this paper takes Japan’s successful promotion of the remote-controlled mower, a smart agricultural machine, as a research case. It systematically analyzes the background, practices, and mechanisms of Japan’s efforts to promote smart agricultural technologies and extracts key lessons for China. The study finds that in recent years, Japan has regarded the promotion of smart agricultural technologies at the grassroots level and the development of smart agriculture as important strategies to mitigate the impact of aging and depopulation on agriculture. The mechanisms enabling the successful promotion of smart agricultural technologies, exemplified by the remote-controlled mower, include four aspects: constructing a coordinated promotion network with both “vertical connectivity” and “horizontal collaboration,” forming a virtuous cycle of policy, research and development, promotion, application, and feedback, enhancing the professional capabilities of frontline agricultural technicians, and focusing on farmers as the principal agents of technology adoption. Based on the above analysis, the paper extracts four key lessons for China.