Several literature reviews on crowdfunding categorise crowdfunding research into different perspectives but provide limited theory development. The social capital literature offers a promising lens for understanding crowdfunding. We provide a comprehensive review of how internal social capital develops through crowdfunding activities and how both external and internal social capital affect crowdfunding campaign dynamics, including early-stage performance, general process, funding performance and post-campaign performance. Most researchers report a positive but dynamic impact of social capital on crowdfunding activities over time. We apply a dynamic view to develop a conceptual model that explains how external and internal social capital affect crowdfunding campaigns. We conclude with proposed directions for future research, including an analysis of the negative aspects and the causal effects of social capital.