An interesting question concerns how large-scale (mental) health services policy initiatives come into being, and the role of evidence within the decision-making process behind their origins. This paper illustrates the process by which motivation to address homelessness, in the context of the upcoming 2010 Vancouver Olympics, was leveraged into a pan-Canadian project including sites in Vancouver, Winnipeg, Toronto, Montreal and Moncton, New Brunswick. The aim of the initiative was to implement and evaluate an intervention, Housing First, to provide housing and support to previously homeless people with mental illness. This qualitative case study was conducted between December 2009 and December 2010, employing grounded theory, and drawing on archival documents and interviews with 19 key informants involved in the conception of the project. Overall, the findings affirm that policy-making does not follow a rational, linear process of knowledge translation/exchange (KTE) and implementation, whereby evidence-based “products” are brought forward to address objectively determined needs and then "placed into decision-making events" (Lomas, 2007, p. 130). Instead, evidence-based policy making should be understood within the much more complex context of "policy entrepreneurship" (Kingdon, 2003; Mintrom & Norman, 2009) which entails taking advantage of windows of opportunity, and helping to bring together the "streams" of problems, politics, and policy ideas (Kingdon, 2003).