This paper explores the origin, evolution, and appropriation of social capital by new ventures seeking international growth. Using longitudinal case studies in the software industry, we model the dynamic influence of social capital on new venture internationalization. We theorize that new ventures of founders from a globally-connected environment, such as with return migration or MNC experience, have higher stocks of initial social capital than others. We provide a nuanced analysis of the dynamic processes involved in the evolution of social capital, and highlight the mechanisms of decay and replenishment over time. Network learning plays a critical role in new ventures' ability to realize the potential contribution of social capital to international growth.