Despite the abundance of research on motivation in ELT, teachers' motivational behaviors have received scant attention in prior research. Therefore, the current study aimed to investigate the effect of a professional development course with a focus on training teachers how to use motivational strategies based on Kellers' ARCS model on teachers' use of motivational strategies and additionally to explore likely differences between experienced and inexperienced teachers in their use of motivational strategies. The study further aimed to probe the impact of teachers' motivational behaviors on student motivation and their perceptions of their teachers' teaching effectiveness. To this end, 10 teachers and 100 students were conveniently sampled. Data were collected through questionnaires and class observations. The results revealed a significant difference in teachers' use of motivational strategies before and after the professional development course. Teaching experience, however, did not make any significant difference in teachers' use of motivational strategies. Additionally, teachers' use of motivational strategies had an insignificant effect on students' judgments of their teachers' teaching effectiveness but a significant positive effect on student motivation.