The aim of this study is to examine the effect of teaching carried out using the REACT strategy enriched with reflective thinking activities on students' Reflective Thinking. The research was carried out in the first semester of the 2019 – 2020 academic year with students studying at a public school in Istanbul. A quasi-experimental design with control and experimental groups was used in the research. The application was designed by the researcher in the form of 28 lesson hours in total, eight weeks for the "Systems in Our Body" unit. The reflective Thinking Scale was used as a data collection tool in the study. Obtained quantitative data were analyzed with IBM SPSS v22. According to the results of the analysis, a significant difference was found after the application in the pretest and posttest scores of the experimental group students. As a result of the research, it was determined that the students in the experimental group also increased their Reflective Thinking Scale total scores. There was no increase between the Reflective Thinking Scale pretest and posttest scores of the control group students.