A substantial body of literature has highlighted many factors that impede faculty change, the most common of which are a lack of training, time, and incentives. However, there may be other barriers--unacknowledged and unexamined barriers--that might prove to be equally important. In particular, the tensions between a scientist's professional identity and the call for faculty pedagogical change are rarely, if ever, raised as a key impediment to widespread biology education reform. In this article, the authors propose that scientists' professional identities--how they view themselves and their work in the context of their discipline and how they define their professional status--may be an invisible and underappreciated barrier to undergraduate science teaching reform, one that is not often discussed, because very few educators reflect upon their professional identity and the factors that influence it. The authors' primary goal in this article is to raise the following question: Will addressing training, time, and incentives be sufficient to achieve widespread pedagogical change in undergraduate biology education, or will modifying their professional identity also be necessary?