The aim of this research is to determine the misconceptions of students about the subject of the moon and to examine the effects of science lesson with reflective science diaries on the achievements of students and eliminating their misconceptions. The research designed according to the pretest-posttest control group model among the experimental research methods was carried out with the participation of 50 students including 25 experiments and 25 control groups. Lessons were carried out through enabling students to keep reflective science diaries for 6 weeks in the experimental group. As a measurement tool, the achievement test, consisting of 4 open-ended questions, was applied to both groups as pretest and posttest. As a result of the research, a significant difference was observed in favor of the experimental group where reflective science diaries were applied. It was found that students have several misconceptions about the subject of the moon. It was concluded that the reflective science diaries were effective on the students' achievements and on elimination of misconceptions on the topic of the moon.