It is argued that the B Corp certification acts as a third-party signal of social purpose business model innovation. There is increasing schorlarly attention toward understanding how companies, and especially Small and Medium-sized Enterprises (SMEs), seeking responsible impact organize their practices. However, this research has primarly explained the motives and barriers in these strategies and has not fully explored the mechanisms for such change. In addition, academics have studied for decades a useful way of changing practices in SMEs, i.e. through the participation into collective strategies about very different issues such as planification, quality and environmental management. In this paper, we address the following research question : Is the collective B Corp certification strategy a catalyst for SMEs’ CSR commitment? To do so, we conducted an exploratory qualitative case study in Northern France among a group of SMEs which have been implied in a collective B Corp certification strategy. Our contribution is twofold. First, thanks to an auto-ethnography enriched by a questionnaire survey, our results confirm the potential role as a catalyst of a collective strategy in CSR commitment of small companies. Second, we propose managerial recommandations to several actors, i.e. the entrepreneurs, the support networks and the B Corp NGO.