The 1920s and 30s were a high phase of liberal missionary internationalism driven especially by American-led visions of the Social Gospel. As the missionary consensus shifted from proselytization to social concerns, the indigenization of missions and the role of the "younger churches" outside of Europe and North America was brought into focus. This article shows how Protestant internationalism pursued a "Christian Sociology" in dialogue with the field’s academic and professional form. Through the case study of settlement sociology and social work schemes by the American Marathi Mission (AMM) in Bombay, the article highlights the intricacies of applying internationalist visions in the field and asks how they were contested and shaped by local conditions and processes. Challenging a simplistic "secularization" narrative, the article then argues that it was the liberal, anti-imperialist drive of the missionary discourse that eventually facilitated an American "professional imperialism" in the development of secular social work in India. Adding local dynamics to the analysis of an internationalist discourse benefits the understanding of both Protestant internationalism and the genesis of Indian social work and shows the value of an integrated global micro-historical approach.