This thesis addresses two research gaps in the field of Problem-Based Learning (PBL) by investigating four research questions through six experiments conducted in two Chinese schools over two years and nine months. With a sample size of 2,334 students from grades 8 and 9, the study demonstrates the positive impact of PBL on learning outcomes and challenges some aspects of Cognitive Load Theory (CLT). The research also examines the effects of individual PBL elements, highlighting the benefits of collective learning and PBL’s synergistic effects. Moreover, it identifies factors such as prior knowledge, task complexity, previous PBL-like experiences, digital assistance, and pro-PBL family culture that can influence PBL’s efficacy. These findings contribute to the field of PBL research by providing empirical evidence from a non-western cultural context, examining PBL’s individual components, and identifying additional contextual factors influencing PBL efficacy. However, limitations include the generalizability of findings, measurement errors, and causality concerns. Future research should expand the scope of PBL in non-western contexts, investigate individual PBL elements and synergistic effects, measure long-term learning outcomes, and explore family-level cultural factors.