The research questions addressed in this study were: what types of epistemological beliefs do elementary students have; what types of metacognition do elementary students have; and what are the relationships among students' perceived characteristics of constructivist learning environment, metacognition, and epistemological beliefs. A total of 626 students enrolled in sixth, seventh, and eight grades of nine elementary public schools located in Ankara, Turkey constituted the participants of this study. Constructivist learning environment survey (CLES), Junior metacognitive awareness inventory (Jr. MAI), and Schommer epistemological belief questionnaire (EB) were administered to students. Factor Analysis of Jr. MAI revealed both knowledge of cognition and regulation of cognition items were loaded into one factor. Confirmatory factor analysis of EB revealed a four factor structure namely innate ability, quick learning, omniscient authority, and certain knowledge. Regression analyses revealed that metacognition and omniscient authority were significant predictors of personal relevance dimension of CLES. Metacognition was found as the only predictor of the student negotiation. Innate ability and metacognition significantly contributed to uncertainty. This study revealed that the elementary students with different mastery levels hold different epistemological beliefs and multi-faceted nature of elementary school students' metacognition was seemed to be supported with this study. It was found that metacognition contributed to model more than epistemological beliefs for all three dimensions of CLES.