This article traces multiple directions in the evolution of agroecology, from its early emphasis on ecological processes in agricultural systems, to its emergence as a multidimensional approach focusing on broader agro-food systems. This review is timely, as agroecology is being increasingly applied within a diversity of scientific-, policy-, and farmer-based initiatives. We contrast different agroecological perspectives or “agroecologies” and discuss the characteristics of agroecology characterized by a transdisciplinary, participatory and action-oriented approach. Our final discussion describes the contents of the special issue, and states our goal for this compilation, which is to encourage future work that embraces an agroecological approach grounded in transdisciplinarity, participation, and transformative action.