The Kahnawake Schools Diabetes Prevention Project (KSDPP) is an ongoing participatory research and intervention project aimed at the primary prevention of type 2 diabetes. Formally initiated in 1994 with strong community support, KSDPP provides a fertile opportunity to learn about how a community came to identify the need for preventive action on a health problem such as diabetes. The purpose of our study was to describe the various conditions in the community of Kahnawake, which gave rise to its mobilization for the prevention of type 2 diabetes. Qualitative data consisted of 12 individual interviews and one focus group with key community members and health professionals living and/or working in the community of Kahnawake, along with historically relevant documents. The data collection and analysis procedures of the grounded theory method were applied. Results describe a preceding phase to formal KSDPP implementation, triggered by returning research results on the community prevalence of type 2 diabetes. This phase of 'legitimizing diabetes as a community health issue' is characterized by a shift in the perceived preventability of diabetes among community members; from a problem that was to be lived with to a problem that was to be prevented. The shift in perceptions was facilitated by the context in the community, described by structural developments, cognitive and relational elements. In addition to reaffirming the critical importance of utilizing lay knowledge during the planning of a health promotion intervention, our study has uncovered some of the key conditions through which individuals in the community came to participate in the identification and planning of a diabetes prevention project.