Educational authenticity occupies a strong position in higher education research and reform, building on the assumption that correspondence between higher education learning environments and professional settings is a driver of student engagement and transfer of knowledge beyond academia. In this paper, we draw attention to an overlooked aspect of authenticity, namely the rhetorical work teachers engage in to establish their learning environments as authentic and pedagogically appropriate. We use the term "authenticity work" to denote such rhetorical work. Drawing on ethnography and critical discourse analysis, we describe how two teachers engaged in authenticity work through renegotiating professional and educational discourse in their project-based engineering course. This ideological project was facilitated by three discursive strategies: (1) deficitization of students and academia, (2) naturalization of industry practices, and (3) polarization of the state of affairs in academia and in industry. Our findings suggest that authenticity work is a double-edged sword: While authenticity work may serve to bolster the legitimacy that is ascribed to learning environments, it may also close down opportunities for students to develop critical thinking about their profession and their education. Based on these findings, we discuss implications for teaching and propose a nascent research agenda for authenticity work in higher education learning environments.