A persistent challenge for teacher professional development is how to best support the translation of knowledge into practice. Building on scholarship that characterizes teacher learning as both a cognitive and situated process, we examine one district's effort to enact a model classroom approach to professional development. Based on qualitative interviews, observations, and survey data, we find that teachers who engaged in the model classroom in sustained ways reported incorporating specific strategies into their practice. The model classroom had key characteristics that supported teacher learning: the ability of teachers to observe real-life practice with students present and the alignment of model classroom activities to teachers' own teaching contexts. According to teachers' self-reports, these dimensions of authenticity triggered a range of cognitive responses and prompted self-reported changes in teacher practice. Most importantly, how teachers reported feeling during a model classroom visit was related to how much teachers reported internalizing what they observed and how much teachers made plans to incorporate new ideas into their practice. [This is the online first version of an article published in "Professional Development in Education."]