Entrepreneurs and start-ups are key actors in implementing environmental innovation and accelerating sustainability transitions. Thus, analyzing as well as predicting the impact of entrepreneurial ventures is central to management and entrepreneurship research. The sustainability performance, value and impact of incumbent firms and their products and services has been a key topic in business-related sustainability research for many years. However, assessing the sustainability effects of new ventures such as start-ups is a neglected area in the research literature. This article therefore provides an overview, including key definitions, a new conceptual framework, and notions that can help guide and inspire a future research agenda. In this way, it also serves as an introductory article for the Journal of Cleaner Production's special issue ‘Assessing and forecasting the sustainability impact of new ventures: Theories, methods, and empirical evidence’.