This scoping review examines the contributions of farmer organizations (FOs) to smallholder agriculture in sub-Saharan Africa and India. Analyzing 239 studies (2000-2019), the review finds that most studies (57%) reported positive FO impacts on farmer income, but fewer reported positive impacts on crop yield (19%) and production quality (20%). Environmental benefits were documented in 24% of studies. The review suggests that integrating market access, natural resource management, and support for marginalized farmers into FO design and policy could enhance their effectiveness in achieving sustainable development goals.