The aim of this article is to contribute to the ongoing discussion on teacher professionalism by analyzing the professional strategies of Sweden's two teachers' unions from an organizational perspective. Drawing on institutional theory, the article argues that the teachers' unions' focus on strategies of professionalization has as much to do with questions of legitimacy in the eyes of the public, as with any specific effort at transforming the practice of teaching in a professional direction. Against the background of two recent Swedish education reforms, the article shows that the unions are "trapped" within a normative order emphasizing professionalization as the primary way of organizational development and legitimacy, resulting in a need for the unions to adopt professional attributes. In the case of the Swedish unions, this is accomplished through mimetic processes whereby union policies, aimed at the improvement of teaching, are modeled upon the medical profession, regardless of the differences between the technologies and practices of the occupations. In this way, the professional rhetoric of the unions is decoupled from the practice of teaching in order to maximize the public legitimacy needed for improving the declining societal status of teaching.