In the past 5 years, Sport for Development and Social Change (S4SC) organizations have developed a growing interest in social enterprise to support their sustainability. The purpose of this doctorate thesis is to conduct an in-depth analysis in response to this growing interest, asking how does social enterprise support the sustainability of the S4SC organization? To address this question, dimensions of sustainability are first clarified. The role social enterprise can play to support these dimensions and the type of investment this may require are then explained. Fourth Generation realist Evaluation (4GE) underpins the development of this study’s research design. 4GE is a methodology that aims to maintain reciprocal accountabilities between stakeholder groups in the research process. In doing so, this study’s end-users – the SFW network - have driven the trajectory of this study’s iterative design. What unfolds is a journey presented over five phases of study. In the first phase, this study presents how accountability to the study end-users encourages us to renegotiate our conceptualization of social enterprise and sustainability. The latter is presented as a conceptual framework on sustainability. This framework is the most prominent conclusion to be drawn from this doctoral study as it acts as a heuristic, or lens, to make sense of the complex socioecological ecosystems surrounding the S4SC organizations - ecosystems that inform their sustainability. In the final phases, a case study of 3 SFW network organizations is presented to ‘test’ this conceptualization against unique contexts in low and high-income countries. In conclusion, this doctorate thesis makes significant contributions to how we conceive of and action sustainability in the S4SC organization. It highlights the role social enterprise can play and the key factors such as purpose, democratic intention, strategic position and organization ecosystem, and the regulatory environment that may inform what this looks like. Findings from this study also shine light on key resourcing options available to the supporting institutions of the S4SC field and how their investment reinforces key processes of sustainability. Finally, this study’s findings highlight a potential fault line in current conceptual approaches to social enterprise and sustainability. For this reason, concluding remarks provide examples for future research to further explore the foundation set by this study.