This article explores the interplay between different types of knowledge and rationality in care work through a case study of a nursing home innovation project in a Danish municipality. The aim is to understand the implications for innovation processes and dissemination within the context of elder care. Care work, in some sense, relies on relational and contextual knowledge which may lead to challenges when innovation and best practices are to be diffused across organizations. This is especially true since diffusion often relies on codification of practices and knowledge. Caring rationality is essential to how technologies and methods are practiced in the care situation, and thus also essential for best practices and how they are disseminated. However, other types of codified and explicit rationality are equally important. The article concludes that there are several types of knowledge in play in care work practices and innovation, and it indicates that communities of practice could be key to understanding how to share and learn from best practices across organizations.