Impact investors often know their financial return on investments, but are less certain about their impact. This article frames impact as their contribution to sustainable market transformation. A sustainable market transformation consists of inception, first movers, critical mass, and institutionalization phases. Given the nature of such transformations, the impact is effectuated at different moments and toward various market actors. Based on an exploratory research design with semi‐structured expert interviews, this article aims to create an overview of the roles of impact venture capital funds in sustainable market transformations. The results suggest that the view that the capitalization of start‐ups is the only impact of impact investors is a misconception. The needs of companies with sustainability value propositions change over time and consequently impact investors perform various roles. For example, exiting an investment while upholding social and environmental objectives communicates to mainstream business that the start‐up is ready to create a greater impact. Further, impact investors fulfill external roles that change the perspectives of institutional actors toward sustainable investments. Based on an overview of the different roles that impact investors fill, this article proposes a future research agenda to strengthen our knowledge about the impact return of investments.