What can multilevel comparison do in identifying causal mechanisms? Insights from a research on cooperative renewable energy projects in Europe. The search for causal explanations of social processes is a goal shared by many works in the social sciences. This article deals with this issue by showing how a multi-level comparison can contribute to the identification of causal mechanisms. Based on a research on cooperative renewable energy projects in Europe, I first highlight the tools that can be used to deal with the two challenges for identifying and conceptualizing the causal mechanisms: the dilemma of selecting units of analysis and the collection of empirical data, its analysis and explanation of the results. To deal with the issue of the selection of units of analysis, the universe of investigation of the object treated was distinguished, then three levels of analysis were selected to grasp both the structural and strategic dimensions of the observed phenomenon. To deal with the challenge of collecting and analysing the material, on the one hand, the empirical fingerprints were distinguished according to the levels of analysis, put in relation with four types of evidence via the method of process tracing and on the other hand, graphic representations were made to show the identified mechanisms. I then show that multi-level comparison makes it possible to specify the relationships between levels beyond the mechanisms of influence and circulation and that this type of comparison makes it possible to shed light on mechanisms that combine strategic dimensions and structural as well as cognitive mechanisms.