We collaborate with the Chinese Ministry of Agriculture (MOA) and conduct a randomized controlled trial (RCT) to examine the effects of farmer field schools (FFS) on the knowledge acquisition by farmers in rice production in Anhui, China. The intensification of China’s agricultural production has raised widespread environmental concerns. Lack of advisory services to increase awareness and knowledge has been found to be the primary constraint to improving farming and environmental outcomes. However, training millions of small farmers is a significant challenge. To impart the knowledge of sustainable and low-carbon farm management, the MOA recently piloted a FFS program through its public extension system. A participatory approach to rural advisory services, FFS was initiated by the Food and Agriculture Organization during the late 1980s in Asia, and at present is being practiced in more than 90 developing countries. However, the effectiveness of the FFS program has not been conclusively demonstrated, and the results of previous impact evaluations have varied greatly according to evaluation methods. A major drawback of previous studies has been selective participation in the program, leading to biased estimates of program effects. We use an RCT to overcome these problems. The results are heterogeneous: FFS effectively improved farmers’ knowledge of pest management and agro-environment; however, we find no effects on nutrient management and cultivation knowledge. Furthermore, the effects were smaller for female and old participants. Being a “best-design” approach of agricultural extension initiated by FAO, FFS faces challenges to be “best-fit” in China, where urbanization and agricultural transformation are emerging.