Introduction: Classroom misbehavior is a major source of classroom-wasted time and a situation that negatively interferes with students' opportunity to learn. Method: The present study investigated the relation between 5th through 9th grade perceived Portuguese teacher's classroom management, teacher's perceived time spend with misbehavior, teacher's self-efficacy, and teacher's perceived classroom misbehavior. A conditional process analysis of the relation between teacher's classroom management and teacher's perceived classroom misbehavior with mediator and moderator variables was tested. Results: Generically the results show that (1) teachers who perceive themselves as more controllers of students' behaviors tend to perceive less misbehavior in the classroom; (2) that both teacher's self-efficacy efficacy (TSE) and time spent with classroom misbehavior (TSMisb) are better predictors of classroom misbehavior than the classroom behavior management style; (3) both TSE and TSMisb fully mediate the relation between classroom management style and classroom perceived misbehavior. Discussion and Conclusion: Teachers must, therefore, learn the specific behaviors that more likely optimize the available instructional time and reduce time and energy wasted with students' misbehavior.