Aim To report a study of an intermediary programme in infection control practice in one hospital in the UK. Background Promoting best evidence in everyday practice is a constant problem in infection control. Intermediaries can influence the transfer and use of evidence in health care, but there remains a lack of evidence and theory about the specific actions and change processes, which can be successful in improving infection control practices. Design An in-depth mixed methods case study. Methods The study was undertaken in 2011. Participants were recruited through purposive sampling and included frontline staff, managers and nurses in intermediary roles in infection control. Results For frontline staff, intermediary presence triggered a modification in behaviour. Different reactions were noted from the intermediaries' high level of physical presence in clinical areas, the facilitative approaches they used to give feedback and the specific teaching strategies they employed to meet frontline staff needs. The specific intermediary actions uncovered in this study were contingent on the prevailing systems for performance management, organisational commitment and efforts in clinical areas to foster a collegiate environment. Conclusions The study provides theoretical threads of how intermediaries can be successful in promoting evidence use under certain contextual conditions. Further testing of the specific intermediary mechanisms uncovered in this study will contribute to understanding different approaches that work in infection control in embedding evidence in practice.