This integrative literature review takes up the ongoing discussion about the place of mixed methods designs in educational research. We focus on studies that investigate the role of argumentation in inquiry-based learning, either as a means for enhancing inquiry (argument-based inquiry) or as a learning outcome (inquiry-based argument). We argue that this field of research offers a perfect example of the ways in which a paradigm and its research questions call for mixed-methods designs. We then present an integrative review to explore patterns and identify gaps in the literature, asking: (1) How frequently and in what ways are mixed methods used in the field? (2) What rationales are driving the use of mixed methods? and (3) To what extent is the potential of mixed methods research being realized in the field?. For readers studying argumentation in inquiry-based instruction, we hope to open up a critical dialogue about aims and methodologies in the field. For readers interested in mixed-methods designs we hope to offer a case study of how to build a rationale from within a discipline for leveraging the range of mixed methodologies to study a problem. We conclude with recommendations for further research.