Small-scale aquaculture producers in developing countries are facing new opportunities and challenges related to market liberalization, globalization and increasingly stringent quality and safety requirements for their products, making it harder for them to access markets. Collective action through participation in farmers’ organizations (FOs) can provide an effective mechanism to assist small-scale producers overcome these challenges and contribute to and influence modern market chains and trade. Literature on agriculture and aquaculture FOs and case studies of successful aquaculture FOs were reviewed and field research on successful aquaculture FOs in India and Thailand was undertaken to bring together current knowledge on the formation, operation and impact of aquaculture FOs. A range of FOs was examined and potential opportunities for success such as “cluster management” and group certification were highlighted. The publication presents factors associated with successful FOs and guiding principles for development organizations that wish to support aquaculture FOs in developing countries, followed by a summary of challenges and opportunities for the development of small-scale aquaculture FOs.