Metacognition has recently re-emerged as a central focus of educational initiatives. Developing students’ metacognition can improve academic performance by increasing their self-regulation across learning domains. Research has consistently shown that explicit instruction about metacognitive processes is necessary for developing metacognitive thinking. However, teacher readiness and understandings to do so, have not been studied extensively leaving a significant gap in our understanding of teachers’ knowledge of metacognition and beliefs. This sequential explanatory mixed methods study compared pre-service (n = 43) and in-service (n = 45) teachers’ metacognitive beliefs and reported teaching practices. Data were collected through a questionnaire that informed subsequent semi-structured interviews. Non-parametric statistical tests elucidated differences across teaching samples, while qualitative data were thematically analyzed. Both in-service and pre-service teachers reported struggling to implement metacognition. In-service teachers demonstrated practical, concrete knowledge, as well as creative classroom integration of metacognition while pre-service conceptualizations lacked coherence pointing to specific areas where additional support is needed.