This article describes a study measuring metacognition by means of the Junior Metacognitive Awareness Inventory developed in the USA which was then adapted to be used in Turkey. The survey data from 314 middle school students and 589 tenth grade students were collected in two phases to facilitate both the exploratory factor analysis (EFA) and the confirmatory factor analysis (CFA). Furthermore, the reliability analysis of the scores and convergent, discriminant, and subgroup validity coefficients were examined. Findings suggested that the inventory measures two constructs, namely, the knowledge and regulation of cognition. These results demonstrated that the Turkish version of Jr. MAI is a valid and reliable instrument which may serve as useful in guiding future research aiming to understanding students' metacognitive awareness.