With international agencies tapping music as a channel to address the social needs of marginalized populations, this study explored the outcomes of ensemble singing on the health and social integration of street children in the Philippines. Using mixed methods, perceived effects of ensemble singing on the wellbeing and social inclusion of street children were investigated, as well as the challenges of ensemble singing as a type of intervention for the health and social integration of marginalized groups and the implications of such music-based social action research for ensemble performance studies. Although challenges to ensemble singing were revealed by the children, both choristers and facilitators perceived a range of social, physical, psychological, and spiritual benefits. Facilitators reflected on the transformative potential of ensemble singing for the wellbeing of marginalized populations. This investigation anticipates further exploration on the transnational spectrum of ensemble music in relation to health, social inclusion, and music-based social action research.