Political scientists have developed important new ideas for using spatial diagrams to enhance quantitative research. Yet the potential uses of diagrams for qualitative research have not been explored systematically. We begin to correct this omission by showing how set diagrams can facilitate the application of qualitative methods and improve the presentation of qualitative findings. Set diagrams can be used in conjunction with a wide range of qualitative methodologies, including process tracing, concept formation, counterfactual analysis, sequence elaboration, and qualitative comparative analysis. We illustrate the utility of set diagrams by drawing on substantive examples of qualitative research in the fields of international relations and comparative politics.