We know that metacognitive students are successful in school (Sternberg "Instructional Science" 26:127-140, 1998). However, despite the recognition of the role of metacognition in student success, limited research has been done to explore teachers' explicit awareness of their metacognition and their ability to think about, talk about, and write about their thinking (Zohar "Teaching and Teacher Education" 15:413-429, 1999). Therefore, the current study investigates teachers' understanding of metacognition and their pedagogical understanding of metacognition, and the nature of what it means to teach students to be metacognitive. One hundred-five graduate students in education participated in this study. The data analysis results, using mixed research method, suggest that the participant's metacognitive knowledge had a significant impact on his/her pedagogical understanding of metacognition. The results revealed that teachers who have a rich understanding of metacognition report that teaching students to be metacognitive requires a complex understanding of both the concept of metacognition and metacognitive thinking strategies. (Contains 4 tables and 2 figures.)