Professional boundary takes place as actors negotiate occupational boundaries and division of labour. In this article, we examine the conditions of defensive, accommodating, and configurational boundary work in the context of crime investigation. We analyse how professional boundaries are negotiated as civilian investigators become involved with policing. The article is based on 71 interviews with civilian and police crime investigators from a variety of investigation units in Sweden. Findings show how policing as a professional field is shifted as civilians from a wide variety of backgrounds and with varying motivations enter the occupation. Defensive boundary work that devalued civilians was widely occurring. However, boundary work that focused on learning, collaboration, and training was also occurring in high-status units. The discussion focuses on how power asymmetries impact boundary work when professions are undergoing change. This study exemplifies how organizational actors navigate, defend, and challenge their positions as professional boundaries are negotiated.