There is a growing consensus that the adoption of performance measurement tools are of particular interest for social enterprises in order to support internal decision‐making and to answer the demands of accountability toward their stakeholders. As a result, different methodologies to assess the non‐financial performance of social enterprises are developed by academics and practitioners. Many of these methodologies are on the one hand discussions of general guidelines or, on the other hand, very case specific. As such, these methodologies do not offer a functional tool for a broad range of social enterprises. The goal of this article is to fill this gap by developing an instrument suitable for the internal assessment and the external reporting of the non‐financial performance of a diverse group of social enterprises. To reach this goal, we used qualitative (focus groups and a Delphi panel) and quantitative research methods (exploratory and confirmatory factor analysis), involving multiple actors in the field of social entrepreneurship. Focusing on five dimensions of organizational performance (economic, environmental, community, human and governance performance), we offer a set of indicators and an assessment tool for social enterprises.