Relying on the hybrid organization literature and the circular economy literature, our study aims at theorizing how hybrid organizations adopt circular economy business models to contribute to sustainable development. Through six in-depth interviews with social entrepreneurs located in different regions of Italy and operating in different industries, we theorize that four aspects are unique to hybrid organizing that adopt a circular economy business model. We find that hybrid organizations foster sustainable development thanks to their ability to develop and maintain relationships with the surrounding organizational realities. Additionally, we find that hybrid organizations contribute to sustainable development thanks to their motivation to guard and watch over the natural environment and human beings. In addition, we find that hybrid organizations foster sustainability by educating, spreading knowledge, and ennobling the human spirit. We therefore present a conceptual model that shows how hybrid organizations that adopt circular economy models contribute to sustainable development. In sum, our findings expand on previous literature, add new knowledge, and integrate fields of research that usually develop in silos.