ABSTRACT
Despite the value of inter-organizational collaboration in mission achievement, clarity on the internal “process” dimension of collaborative activity remains elusive and understudied compared to other partnership dynamics. This study offers the first comprehensive review of the multidisciplinary literature on nonprofit collaboration processes, examining 253 empirical studies. We introduce a three-dimensional framework to guide our review, focusing on how scholars have conceptualized the collaboration process and chosen their strategies of inquiry. Our analysis identifies patterns across ontological, epistemological, and methodological approaches to studying this dynamic concept. We present six recommendations for future nonprofit and voluntary sector studies, highlighting how the dual meaning of the collaboration process and the variation in theoretical frameworks influence research strategies, how the temporal aspects of the collaboration process are often overlooked, and how variability in methodological quality, representation gaps in data, and the scarcity of engaged scholarship can limit our understanding of the internal dynamics of partnership formation and management.