Problem-Based Learning has been recognized as a fundamental approach in Science Education. Studies show that the success of this approach depends on students’ ability to self-regulate their learning and on teacher feedback. However, research on how these aspects interact in formal science teaching contexts remains limited. This study aims to address this gap by investigating two questions: What self-regulation strategies are used by different student groups while solving a problem on water hardness? How does teacher feedback influence the problem-solving process? The study involved 27 students and their Physics and Chemistry teacher. Students participated in an activity that required solving a problem related to water hardness. Data were collected through audio recordings, and the content of the transcriptions was analyzed. The results showed connections between self-regulation strategies and teacher feedback during the problem-solving process. Groups with high participation employed diverse self-regulation strategies, successfully solved the problem, and received varied teacher feedback. The group with the lowest participation received the least feedback from the teacher. Future research should focus on examining how different types of teachers’ feedback during specific interventions for less-participative groups influence the development of their self-regulation strategies.