Development actors are increasingly prioritising ‘investing in women’ to ensure food security and sustainability-as well as equity-in agricultural development. In this context, collective action is a critical but poorly understood way for women small-scale farmers to strengthen their engagement in agricultural markets. This report provides rigorous new evidence, from quantitative and qualitative research carried out in Ethiopia, Mali and Tanzania, on the economic and empowerment benefits of women’s participation in collective action groups across different agricultural farming systems and markets. The success factors and intervention strategies that have enabled women to benefit most are analysed in order to identify lessons for the future. The research highlights gaps in both current development practice and the wider policy environment which need to be addressed to ensure that collective action in agricultural markets is effective and empowering for rural women.