Background: The aim of this study was to gain a better understanding of interpersonal coordination (i.e., covariation over time) in different modalities (e.g., physiology, language) during psychotherapy and their importance for understanding the dynamics of psychotherapeutic interaction and efficacy. Methods: We conducted a systematic review of all studies examining some form of interpersonal coordination in a psychotherapeutic context. Results: We first summarize details of the included studies such as gender composition, therapy types, and methods used. The collation of these studies provided evidence that, during psychotherapeutic contexts, interpersonal coordination occurs in physiology, movements, interpersonal displays, and language/vocalizations. Further, it also showed that movement coordination was most frequently associated with psychotherapy outcomes, physiological coordination was most frequently associated with empathy, and coordination in a variety of modalities including language/vocalizations were most frequently associated with therapeutic alliance. Conclusions: We discuss these results, shortcomings with the current literature, and highlight three crucial questions for future research. Research on interpersonal coordination in psychotherapy has potential to advance the both the research and practice of psychotherapy.