Metacognition is an invaluable part of instruction of higher order thinking (HOT). The goal of this article is to review previous studies about teachers' knowledge and professional development (PD) in the area of metacognitive instruction in the context of teaching HOT. Part A of the article reviews 25 empirical studies assembled through a scoping review. Although each individual study consists of significant findings, our analysis indicates that, "as a field," the study of teachers' and pre-service teachers' knowledge in this area is still rather preliminary and exploratory. The review draws several conclusions regarding the nature of the research in this area. However, lack of a common conceptual framework and research instruments precludes the possibility of drawing meaningful general conclusions from the findings of the 25 studies. Part B centers on 8 empirical and theoretical studies addressing the same conceptual framework centering on meta-strategic knowledge (MSK). The findings demonstrate the significance of metacognition in general, and MSK in particular for teachers' ability to teach HOT, showing that it can be developed in both pre-service and in-service teachers' education and PD. The findings highlight several specific characteristics of teachers' knowledge and learning processes in this area. Yet, the findings also show that metacognition is rarely addressed in a satisfactory manner in large-scale efforts to teach HOT and that MSK is mostly neglected in PD programs for teaching inquiry learning. The implications for research and practice of HOT and metacognition are discussed.