Social economy organizations (SEOs), designed to do good for society, have been attracting significant attention as an alternative to purely profit-driven businesses. However, the sustainability of these hybrid organizations has been questioned due to the challenges in meeting the dual bottom-lines of financial performance and social purpose. This article takes a causal-process tracing (CPT) case study approach and analyzes eight SEOs to investigate the common characteristics of sustainable SEOs. The results of the analysis show that effective leadership is a sufficient (but not necessary) condition for the survival of SEOs, while leadership is a necessary (but not sufficient) condition for SEOs' thriving. Business competitiveness is found to be necessary for SEOs' long-term success and performance over time. Collaborative networking is a contributory condition for SEOs thriving but not a necessary condition for their survival.