Complementarities between crop and livestock systems are increasingly emerging as levers for the development of sustainable production systems. At the territory level, between specialized farms, these complementarities make it possible to recreate a functional diversity between systems, while benefiting from the advantages of individual specialization. Various projects have emerged in recent years and are attracting the interest of actors of agricultural sector, territories and research. This article presents a synthesis of the factors of success or lock-in of these projects, through an analysis of the trajectories of several case studies. The factors identified are of varied nature: technical, organizational, social. Several avenues have been identified to strengthen and sustain these projects. They involve actors in the agricultural sector, but also territories, each with an important role in the dynamics of change.