Classroom discipline is a significant concern in most educational systems and a critical element of an effective learning environment. In this article, we present a multilevel analysis of teachers' perceived classroom discipline (PCD) in Portugal, using data from the TALIS 2013. Portuguese teachers perceived slightly more classroom discipline problems than the mean of OECD countries, with classroom variables explaining PCD much better than school-related variables. The percentage of low achievers in the classroom, teacher's self-efficacy, and teacher's need for training in classroom management were the best predictors of PCD. Still, student-related factors (e.g., low achievement) were better predictors of PCD than teacher-related factors (e.g., teacher experience or teacher gender).