Te professionalization of evaluation means diferent things to diferent people, and as a result, the feld lacks a clear understanding of how to empirically assess evaluator professionalism. Tis exploratory study used a sociological model to study the behaviours of practicing evaluators in Canada and the United States using fve concepts: expertise, ethical disposition, professional autonomy, innovation and research, and credentialing. Results from 27 in-depth interviews and a survey of 456 respondents demonstrated that, depending on their demographic characteristics, perceptions of professionalism difered between evaluators in the two countries. Te study determined that theory-based sociological models can provide insights into the professionalization of program evaluation.