This paper explores the professionalization project of paramedics, based on an ethnographic study of UK National Health Service (NHS) ambulance personnel. Drawing on concepts derived from institutional theory and the sociology of professions, we argue that the project is enacted at two levels, namely a formal, structural and senior level reflecting changing legitimation demands made on NHS practitioners and pursued through institutional entrepreneurship, and an informal, agentic, ‘street level’ enacted by the practitioners themselves via ‘institutional work’. Focusing on this latter, front‐line level, our ethnographic data demonstrate that the overall impact of the senior level professionalization project on the working lives of paramedics has been somewhat muted, mostly because it has had limited power over the organizations that employ paramedics. Given the slow progress of the senior level professionalization project, paramedics at street level continue to enact subtle forms of institutional work which serve to maintain ‘blue‐collar professionalism’ – a form originally identified in Donald Metz's ethnography of ambulance work. Our analysis draws attention to the complex and contested nature of professionalization projects, in that their enactment at senior and street levels can be somewhat misaligned and possibly contradictory.