The present work provides a review of two widely used approaches in educational research: action research and case study. Action research aims to improve educational practice by means of reflective cycles and shows variants according to a predominant paradigm, from technical to critical visions. A case study, described as an umbrella term, focuses on understanding classroom situations in real contexts. Although it seems that the defining characteristics of the case study are common among different authors, there are numerous classifications, which sometimes overlap. Based on a review of the ideas forming the main cornerstones of these two research types, we have analysed their common points and differences and considered the methodological possibility of relating both approaches in educational research projects taking place in non-controllable situations. In the present work, two joint approaches are proposed: action research as collective case study and action research as a set of case studies. The possibilities and limitations of both methodological perspectives are also discussed.