Teaching methods and strategies play an important role in encouraging students' active participation in learning and thinking, skills, knowledge, and attitudes, and they have a strong influence on students' learning outcomes and practices to help develop students' personalities. However, most teachers still use teaching methods that are not up to date with the new era (e.g., teacher-centered approach), which leads to students being inactive, not united and cooperative, not communicating well, not having critical thinking, not having problem solving skills, and having incomplete knowledge. The purpose of this research was to find out reasons for using blended learning to help students be active in their studies and to improve their achievement in science subjects in Grade 3. There were 19 students (five females) and four observers (four females) who participated in this study. Research tools such as observation checklists and interview guides were developed, and data were analyzed using thematic analysis. Pre-test and post-test and observation checklists were analyzed by Microsoft Excel, focusing on descriptive and inferential statistics. The results showed that blended learning helped students to be active in learning by improving lesson objectives, teaching materials, teacher methods, student learning behaviors, student satisfaction, and participation. Concerning learning activities, self-study at home with the help of parents or guardians helped improve students’ learning outcomes (Mean pre-test = 1.61, SD = 0.89 and Mean post-test = 6.82, SD = 1.74). The t-test results showed a significant difference (p<0.05), meaning that the results are 95% reliable. Overall, the use of blended learning has helped students to be active in learning and improving their academic achievement in science subjects in Grade 3.