This study investigated the role of EFL teachers' classroom discipline strategies in their teaching effectiveness and their students' motivation and achievement in learning English as a foreign language. 1408 junior high-school students expressed their perceptions of the strategies their English teachers used (punishment, recognition/reward, discussion, involvement, and aggression) to discipline the classroom. The students evaluated their teachers' teaching effectiveness by completing effective Iranian EFL teacher questionnaire (Moafian, & Pishghadam, 2009). They also filled in Attitude/Motivation Test Battery (GhorbanDordinejad & ImamJomeh, 2011) that assessed their motivation towards learning English as a foreign language. Achievement in English was established based on formal grades students received at the end of the academic year. The results showed that EFL teachers reward and praise students for good behavior and they are not very authoritarian. Further, teaching effectiveness, motivation and achievement in learning English were all found to be related to discipline strategies. The results of path analysis showed that those teachers who used involvement and recognition strategies more frequently were perceived to be more effective teachers; however, students perceived teachers who used punitive strategies as being less effective in their teaching. It was also revealed that in classes where teachers managed disruptive behaviors by using punitive strategies, students had problems in learning as punitive strategies lowered students' motivation. Teaching effectiveness was found to mediate the effect of punishment on motivation while motivation mediated the effect of punitive strategies on achievement. Motivation was found to have the strongest effect on achievement.