In this article, I outline the foundations of a consistent and systematic approach to conceptualizing communities in action-oriented sustainability research. More specifically, I develop a conceptual heuristic based on key questions related to ontology, epistemology, methodology and motivation that should be useful for researchers regarding the process of initiating, clarifying and reporting on research with communities. While the use of the community concept in sustainability research is particularly prominent, variability in the possible types of social groupings combined with the concept’s long and complicated etymology in the English language means the community concept lends itself easily to ambiguous and unspecified use. This can lead to problems of both conceptual vagueness and concept-object mismatch in scientific research, which in turn can influence the applicability and efficacy of research outcomes. While problems with community conceptualization are generally recognized, the heuristic developed here contributes by providing researchers with a framework and procedure for addressing these persistent challenges. The heuristic supports the rational and systematic development of a community concept that is sensitive to concrete contextual characteristics, while maintaining roots in a consistent philosophy of scientific knowledge production.