The RECOTTE project deals with the ecological transition at the local cross-border level. This issue is one of European priorities such as the Green Deal, which sets out the directions to be taken to address climate change. Although each Member State has drawn up its own National Climate Energy Plan, there are differences between territories in the application of these policies, which makes their articulation at a cross-border level complex. In addition, the municipalities seem to be insufficiently prepared to take the turn of the transition. The RECOTTE project builds a methodology to strengthen potential cross-border synergies based on the identification of local transition challenges that are convergent and complementary on both sides of the border, and co-construction with local actors of leveraged projects in order to carry out joint transitional actions.