This study has two aims. The first is to determine the effect of argumentation and epistemologically enriched argumentation on academic achievement. The second is to determine students' opinions about the effect of the integration of argumentation and epistemologically enriched argumentation into the teaching process on academic achievement. In this regard, a mixed research method was utilised in the study. The sample consisted of 98 seventh-grade students studying in public schools in Turkey. The quantitative data of the research were collected using an achievement test. The qualitative data were collected by semi-structured interviews with 12 students selected from the experimental groups. There were two experimental groups in the study. Students in the first experimental group learned the "Structure and Properties of Matter" unit by the integration of conventional argumentation into the teaching. In the second group, students learned the same topic through epistemologically enriched argumentation. In the comparison group, the Turkish National Science Curriculum was used with no integration of argumentation. In the study, it was determined that the students in both experimental groups were more successful than the students in the comparison group. The findings of the research are discussed considering the related literature and suggestions were given.