Complexity theory has previously been used as a conceptual lens in human healthcare research. Antimicrobial stewardship (AMS) is an inherently complex healthcare intervention; however, the extent to which complexity has been operationalized in AMS is currently unclear.To investigate if, and how, complexity theory has been used to inform AMS in human healthcare.Scoping review methodology. Empirical research or policy specifically referencing complexity in relation to AMS were considered in any human healthcare setting and geographical location. Databases searched were: Cinahl, Cochrane Library, Embase, Medline, National Institute for Health and Care Excellence, PsycInfo, Scopus and Web of Science from inception to June 2020. Grey literature and other databases searched: EVIPNet, Google, Mednar, Proquest Theses, and the World Health Organization library of national antimicrobial resistance action plans. Non-English language articles were excluded.Of 612 records retrieved, 8 articles were included. Heterogeneity in study design and geographical location were noted. Three interventional studies evaluated AMS in hospital (n = 2) and long-term care (n = 1) settings. Remaining studies were non-interventional and proposed AMS strategies conceptualized through complexity theory. The importance of close engagement between researchers or policy administrators and the target population was emphasized in all studies, as a means of ensuring AMS relevance and success.There is a paucity of AMS research informed by complexity theory, and no policy documents could be located using complexity as a guiding theory. Mixed methods, informed by complexity theory, is a potentially suitable strategy to develop, implement and evaluate AMS as a complex intervention.