Across contrasting farming and sustainability context worldwide, social actors are mobilizing to promote agroecology in order to meet the major challenges of sustainable development, such as food security, halting biodiversity loss, employment and climate change adaptation. Whether on a national or territorial scale, public action initiatives are experimenting the development of food systems based on agroecological practices. Nevertheless, these initiatives are quite diverse (oriented towards production or consumption, trade promotion, environmental protection, value chain dynamics at national or territorial levels) and do not provide a systemic agroecological centred response to the challenges of production, employment, environment and public health. Moreover, these initiatives remain limited, often on a much localized spatial and temporal scales. At present, multiple discourses support agroecology, however, it has not reached a level of credibility that would allow the development of policies that form the basis for transforming food systems towards greater sustainability and resilience at the speed required. In many countries, the decision to move towards an agroecological transition is a major break with the policy directions taken for several decades, based on the green revolution. While public policies are key drivers to support and enable the transition to agroecological food systems, little is known about how these policies should be constructed to be effective. Most research projects focus on assessing agroecological practices at the farm level, and there is no generic framework for analysing how public policies might facilitate or hinder the agroecological transition. The main objective of the TAFS project is to engage with policy makers and provide them with convincing arguments grounded on scientific evidence, field data and concrete experiences, on the appropriate ways to promote agroecological transitions through public policies at different levels. Through different case studies in eleven countries on three continents (Madagascar, Mali, Senegal, South Africa, Lao PDR, Vietnam, India, Argentina, Brazil and Colombia), TAFS will analyse a diversity of socio-ecological and productive contexts with regard to agroecological practices and trajectories. The research design includes six interconnected stages with a diversity of research instruments. The wide range of countries and contexts will facilitate the co-construction of a comprehensive understanding and knowledge about the diversity of agroecological transition processes and how related adapted policy frames may support sustainable food systems in the short and long term.