Few studies examine post-harvest fish losses using a gender lens or collect sex-disaggregated data. This mixed-methods study assessed fish losses experienced by female and male value chain actors in a fishery in western Zambia to determine who experiences losses, why, and to what extent. Results indicate that participation in the fishery value chain is gendered and most losses occur during post-harvest activities. Discussions with fishers, processors, and traders suggest the value chain is more fluid than often depicted, with people making calculated decisions to sell fresh or dried fish depending on certain conditions, and mostly driven by the need to avoid losses and attain higher prices. The study shows that gender norms shape the rewards and risks o ered by the value chain. This could be the reason why a greater proportion of women than men experienced physical losses in our study sample. Female processors lost three times the mass of their fish consignments compared to male processors. Technical constraints (lack of processing technologies) and social constraints (norms and beliefs) create gender gaps in post-harvest losses. Addressing unequal gender relations in value chains, whilst also promoting the use of loss-reducing technologies, could increase fish supply and food security in small-scale fisheries.