This paper examines how agency and structure interact to influence the changing nature of careers in the French Humanitarian Sector – a sector that is undergoing a significant shift towards increased professionalization. Drawing on Giddens structuration theory, the study uses the concept of career script as a dynamic framework to understand both career stability and change. Data was collected at both an individual and organizational level to identify three careers scripts in operation in the field and examine the ways in which they evolve over time. The paper provides an analysis of the power relations involved in the development of career scripts and the professionalization of the humanitarian sector, suggesting a potentially greater role for agency than is typically acknowledged. Finally the paper concludes with a consideration of the wider implications for the study of career change in the future.