This study aims to investigate the effect of Toulmin argumentation model (TAM), epistemologically enriched Toulmin argumentation model (EETAM), and method suggested in Turkish Science Curricula on the epistemological beliefs of 7th grade students and their views on this effect. In this context, while the students in TAM group learned seventh grade structure and properties of matter unit through TAM; the students in EETAM group learned seventh grade structure and properties of matter unit through TAM and then had explicit discussions about epistemological belief dimensions. In the comparison group, students followed national science curriculum and learned the same science topic through the method suggested in curriculum. Students' epistemological beliefs were determined with epistemological belief scale. Also, students' opinions about the effect of TAM and EETAM were determined by semi-structured interviews. Therefore, embedded design of mixed method researches was used. Two experimental and one comparison groups were included. The sample of the study consisted of 98 students studying in a public school in Kayseri, Turkey. As a result of the study, there was a significant difference only between the EEAM group and the comparison group in terms of epistemological beliefs. The same results were reached in the qualitative findings. Therefore, it can be said that explicit discussions on epistemological beliefs is more effective than inquiry-based teaching and method suggested in Turkish national science curriculum. Thus, results expose that explicit teaching of epistemological beliefs helps students better understand epistemic nature of scientific knowledge and learning.