Purpose: This study was conducted with students in their third year at the Department of Science Teaching at Kastamonu University in the 2015-2016 academic year. The objective of the study is to investigate the effect of argumentation-based inquiry approach and argumentation-based inquiry approach supported by metacognition activities on science achievement of students. Design/Methodology/Approach: The study was carried out in 10 weeks with the participation of 69 students divided into three

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... ups, namely, the ABI group, the ABI + metacognitive activity group and the group in which the traditional method was applied. An achievement test consisting of 25 questions and semi-structured interviews were used as data collection tools. Findings: The data obtained showed that there was a significant difference between the groups, which was in favor of groups where the ABI approach was applied, and that there was a slightly significant difference between groups of ABI and the ABI supported by metacognition activities, which was in favor of the ABI group supported by metacognition activities. The interviews with students revealed many important and positive outcomes; the students stated that they were satisfied with the ABI applications, that they would prefer ABI in their professional lives, and that the applications facilitated the scientific thinking process. Highlights: Metacognition has an important place in scientific literacy and structuring of knowledge. Because it provides metacognition to be aware of the individual's own learning and learning process. It can be said that language practices such as discussion and writing, especially in the ABI process, activate cognitive and metacognitive mechanisms.