The participatory market chain approach (PMCA) is a methodology for improving the performance of poorly-coordinated value chains. This study uses a mixed methods approach to assess the effectiveness of PMCA for promoting aquaculture value chain development in Bangladesh and Nepal. The study consists of a quantitative structured survey and two story-based qualitative methods, Most Significant Change analysis, and SenseMaker® research software. Quantitative results show that in both countries the PMCA intervention significantly increased the quantity of fish produced, consumed and sold by participating households, leading to an approximate doubling of yields and income from fish. Qualitative findings indicate that PMCA fostered better access to markets for inputs and end products among market chain actors of all types, and improved their coordination and collective decision making, thereby somewhat rebalancing the dynamics of trade relationships to empower small producers.