While previous research has shown that claim-evidence-reasoning can effectively promote higher-order thinking skills in science education, more research should be done on using claim evidence-reasoning in elementary school settings. This study aims to investigate the effectiveness of claim-evidence-reasoning in promoting the scientific reasoning skills of elementary school students. The study utilized a convergent mixed-methods quasi-experimental design, incorporating both quantitative and qualitative data. The participants were 29 Grade 5 students. The discussion lasted for 12 meetings. The quantitative data were collected through a pre-test and post-test, which measured the students' performance in claim, evidence, and reasoning categories. The qualitative data were gathered through open-ended questions that asked the students about their experiences. The results showed a marked improvement in all three categories of claim, evidence, and reasoning in the post-test compared to the pre-test. The number of students scoring 0 points in each category decreased significantly, while the number of students scoring 2 points in each category increased. The post-test mean (M=4.31) was significantly higher than the pre-test mean (M=2.34). Furthermore, the qualitative data supported the quantitative findings, indicating that the claim-evidence-reasoning framework helped students connect the learning materials and concepts they learned in class and organize their thoughts before writing their explanations.