Despite the growing emphasis on integrating collaborative problem-solving (CPS) into science, technology, engineering, and mathematics (STEM) education, a comprehensive understanding of the critical factors that affect the effectiveness of this educational approach remains a challenge. This study aims to identify effective strategic and behavioral factors in course design and assess how these factors contribute to students' learning performance. This study collected data from 106 students enrolled in seventh-grade science classes by using a mixed-method approach. First, the t-test results indicate that students' learning performance was improved through CPS-based STEM learning. A path analysis shows that CPS awareness and several behavioral factors had direct effects, while several strategic factors had indirect effects on the improvement of learning performance. Finally, a dialog analysis indicates that students' integrative use of CPS skills, especially "task regulation skills" used along with other skills, helped improve learning performance. This study not only bridges the gap in understanding the effectiveness of CPS in STEM education but also provides specific suggestions for improving instructional design.