This systematic review covers the extant literature on corporate governance in entrepreneurial firms. Using a sample of 137 research papers published from pre-1990 through June 2018 in 60 journals, we categorize outlets, research methods (quantitative, qualitative, review, and non-empirical), theoretical perspectives, and research questions, highlighting key patterns. We then summarize the concepts under study in the sample literature, and the geographical sources and model specification of quantitative empirical studies. The conclusion highlights the quite fragmented nature of the field and the substantial knowledge gaps, and then proposes an actionable agenda for future research in terms of theories, research questions, research settings, and research designs. In particular, we describe the need to explore how corporate governance mechanisms interact with one another and affect firm outcomes, by applying novel theoretical perspectives and methods that could provide a better understanding of entrepreneurial firms' functioning.