This paper delineates the intellectual history of endeavours to generate a unified science of child welfare in Finland in the early twentieth century by elucidating the efforts of leading Finnish protagonists to depict the concept of child welfare science. The idea of such a new science was not unique to Finland; similar trends emerged extensively throughout the industrialising world, in which child welfare was being increasingly championed. The fundamental reasons given for developing a child welfare science in Finland were linked with ambitions to develop child welfare as a consistent system in modern society. The aspiration to develop a scientific basis for child welfare was not only about adapting relevant research-based knowledge to practice, but also about creating historical and theoretical self-understanding in the field. The intention was to construct a comprehensive conceptual framework for the child welfare needed in policymaking, legislation, and systems building, as well as in the development of professional practices. Although focusing on Finland, the review is of more general significance.