The study of nonprofit advocacy has evolved significantly over the past two decades, yet gaps still remain in our understanding of the processes and roles of nonprofit organizations in policymaking and policy change. In part, these gaps may be exacerbated by limitations in the methodologies and research designs used to examine advocacy, despite the growing scholarship base. To investigate this possibility, this article reports the findings of a systematic literature review of 264 scholarly articles that examine the antecedents, processes, and/or outcomes of nonprofit advocacy. The sampling method relies heavily on scholarship published in six leading nonprofit and public administration journals. Although theory suggests that nonprofit organizations have a vital role in facilitating policy processes, much of the advocacy research relies upon a limited form of research questions and methods. Findings also reveal a need for greater precision in describing data, design, and methods, and suggest a need for clearer, validated measures of both nonprofit advocacy efforts and the resulting outcomes. Finally, we suggest new areas for nonprofit advocacy research, including investigating new venues, different levels of analysis, employing emerging research methods, and examining advocacy over time.