In this study, it was aimed to examine the effects of the argument-based science inquiry (ABSI) approach used in the unit of "Reproduction, Growth, Development in Living Beings" on the academic achievement levels of students. The sample of the study was composed of a total of 88 students at Dilek Özer Secondary School in the Nilufer district of Bursa. The study was carried out with three 6th grade classes. Two of these classes were determined as the experimental group and one class was chosen as the control group. In the study, while the experimental group was taught the unit of "Reproduction, Growth, Development in Living Beings" in accordance with the ABSI method, the control group was not intervened in any way. The study was completed in five weeks. Prior and subsequent to the study, a pre-test and a post-test were administered with the aim of collecting data. The mixed method was employed in the study. In order to collect qualitative data, the lessons taught in the experimental and the control groups were tape-recorded. Then, the sets of data obtained from the sound recordings were converted to tables by making content analysis. The sets of quantitative data obtained in the study were compared by using the 'independent samples t-test' and the 'dependent samples t-test' in the spss program. As a result of the analysis of the sound recordings, while the rate of teacher dialogues was low and that of student dialogues was high in the experimental group, the opposite was observed in the control group. Moreover, while there was not a significant difference between the experimental and the control group in terms of the mean scores obtained from the achievement test, a significant difference was found between the experimental group's pre-test and post-test score means.