Metacognition, or the ability to be consciously and intentionally aware of one's thinking and the ways in which one's thinking impacts one's learning, has been shown in the research to be a critical component of learners' abilities to learn effectively. One area of research on metacognition has focused on the role of metacognition in video games, specifically in massively multiplayer online games, known as MMOs. Through examples of metacognition in a popular video game such as World of Warcraft or in Adventure Academy, a new educational MMO for children ages 8–13 years old, this chapter highlights the ways in which MMOs can act as spaces that support the development of metacognitive behaviors through the components of planning, monitoring, control, and evaluation, toward improving learning overall.