Abstract: Actors in the agri-food system are increasingly urged to more sustainability, but actions to organize the system's sustainable development encounter difficulties, such as overcoming trust between actors, aligning different views on sustainability or finding the right tools to monitor sustainable development. This suggests that more guidance is needed. Initiated by an open demand from leading actors of the Flemish agri-food system, the objective of this research is to understand the myriad of sustainability assessments in the agri-food system at different levels. First, we start from the actors in our case through elucidating their expressed needs regarding sustainability assessment and through noting which approaches they actually use to pursue sustainable development. We define two building blocks for sustainable development and use them to structure the various approaches actors follow to achieve sustainable development. For our case, we obtained five models to structure current, potential or desired sustainability assessment approaches. This structuring allows reflections at the macro (food system) and micro (industry or firm) level, which facilitates understanding the long term as well as short-term sustainability goals in the complex context of an agri-food system. We conclude that sustainability assessment and interaction between chain actors as equally important main drivers for the sustainable development of the agri-food system, and understanding how they interfere helps guiding and steering complex sustainable development processes. (C) 2018 Published by Elsevier Ltd.