This working paper is a collaboration between two CGIAR Research Programs (CRPs): Fish Agri-Food Systems (FISH) and Roots, Tubers and Bananas (RTB). It documents linkages between fish, roots, tubers and bananas (RTB crops) within food systems; identifies opportunities for strengthened integration in production systems, animal feed and nutritional products; and identifies constraints and research gaps, and provides policy recommendations that support nutrition-sensitive food systems. It also looks into integrated aquaculture—agriculture (IAA) food systems globally, before focusing on two specific countries: Bangladesh and Nigeria. The research is mostly based on peer-reviewed publications, though it is complemented with illustrative accounts from academic professionals, farmers and consumers.