This study investigates interactions between a novice language teacher and TESOL practicum mentor during a series of post-observation meetings, focusing on how and why the teacher engages in complaining. We draw upon conversation analysis and narrative analysis to look at how the teacher’s complaints are developed and managed, as well as what they accomplish, within the institutional context. The data show the novice teacher uses a variety of interactional resources to construct complaints about her co-teacher, a peer observer, and the practicum course workload. We argue that complaints are relevant to reflective practice and show how the teacher’s complaints work to express beliefs about teaching and learning and to defend her competence and moral values as a novice teacher. Based on our analysis, we discuss implications for mentor practice.