This systematic review offers evidence on the impact of farmer field schools (FFS). It synthesizes quantitative evidence on intervention effects using statistical meta-analysis, and qualitative evidence on the barriers and enablers of effectiveness using a theory of change framework. Roughly 25% of projects covered by this review targeted youth, and 50% targeted women. In spite of the small base of rigorous impact evaluation, the research suggests that FFS are beneficial in improving intermediate outcomes relating to knowledge learned and adoption of beneficial practices, as well as final outcomes relating to agricultural production and farmers’ incomes. While some evidence suggests FFS programs should target younger farmers, those with greater land endowments, and women (favoring those with relatively low opportunity costs of labor and/or farmers with relatively high pesticide costs), research also suggests field schools to be less effective if women are from households where they are not in a decision-making position, or when youth are not able to dedicate their time to the FFS plot or their fields.