Students possess alternative conceptions of many science topics, and these conceptions can act as obstacles for learning scientific concepts. In the field of biology education, students' alternative conceptions of evolution have been widely investigated. However, there is little research on how teachers diagnose and deal with these alternative conceptions, although these abilities are a crucial part of teachers' pedagogical content knowledge. Additionally, little is known about how these abilities are connected to professional experience and content knowledge. Thus, our study investigated how (prospective) biology teachers at various points in their teaching careers diagnosed and reported dealing with alternative conceptions. Therefore, 182 preservice biology teachers, biology teachers in practical training, and in-service biology teachers were surveyed using a questionnaire. The participants were confronted with students' explanations of evolutionary phenomena, most of them based on common student conceptions, such as anthropomorphism, teleology, and essentialism. These student conceptions are rooted in cognitive biases and are common in evolutionary and other contexts. We found that the participants diagnosed only approximately half of the alternative conceptions, with the in-service teachers diagnosing significantly more of the alternative conceptions than the preservice teachers. Furthermore, the analyses revealed a variety of ways to deal with student conceptions. The in-service teachers more often suggested scientifically correct approaches that address student conceptions, whereas the preservice teachers more often did not respond or responded incorrectly. Moreover, the ability to diagnose and deal with alternative conceptions correlated with teachers' content knowledge regarding the topic of evolution and their acceptance of evolution.