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 aquaculture products, making it harder for smallscale producers 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 (such as farmer societies, cooperatives and community-based organizations) were examined and potential opportunities for success such as "cluster management" and group certification were highlighted. Cluster management has proved successful in many developing countries and refers to a group of aquaculture farmers or FOs that collectively implement certain production standards. Recent field experience shows that cluster management used to implement appropriate better management practices (BMPs) can be an effective tool for improving aquaculture governance and management in the small-scale farming sector, enabling farmers to work together, improve production, develop sufficient economies of scale and knowledge to participate in modern market chains, increase their ability to join certification schemes, improve their reliability of production and reduce risks such as disease. The experience of the National Centre for Sustainable Aquaculture's farmer societies and clusters in Andhra Pradesh, India, shows the potential that cluster management has for benefiting small-scale aquaculture farmers. The publication presents factors associated with successful FOs and guiding principles for development organizations that wish to support aquaculture FOs in developing countries that were distilled from the literature and case studies, followed by a summary of challenges and opportunities for the development of small-scale aquaculture FOs.