The Food Systems for Healthier Diets (FSHD) program is a flagship under the A4NH CGIAR research program. It seeks to contribute to healthier diets for poor and vulnerable populations through a better understanding of food system-diet dynamics and through identifying and enabling innovations in value chains and policies. The present study aimed to systematically and methodically document, analyze, and synthesize the FSHD program’s key learnings that emerged over the course of its implementation (2017-2022). This “learning journey” captured lessons learned within and between FSHD Clusters of Activities and within and between four focal countries (Bangladesh, Ethiopia, Nigeria and Vietnam). A combination of document review, interviews (with program team members, key researchers and country coordinators), an online survey (among research partners in the focal countries) and consultative workshops was used to collect these lessons. This report presents the lessons learned across nine learning questions. It provides conclusions on food systems research for healthier and sustainable diets, as well as on programming for this type of research, to help nurture future food systems research.