Nurse practitioners (NPs) were introduced into the Canadian health system almost half a century ago. Despite early evidence of their effectiveness, it took decades to establish a substantial critical mass of NPs. Using the NP as a case study exemplar, we adopted a whole system change perspective to understand what else besides evidence was needed to ensure the success of desirable health systems innovations. We identified elements of whole systems change to analyze literature on the NP movement in terms of leverages, blockages, and system dynamics. Results suggest that evidence was only one of many factors shaping the uptake of NP services as part of larger, ongoing, adaptive whole systems change. The changes required to integrate the NP role within the health system reflect a socio-ecological perspective that may be used to understand sustainable health systems innovation and improvement.