The study addresses the problem of enhancing prospective teachers’ mathematics pedagogical content knowledge. Conducted in 2023/2024 in Manado, Indonesia, it examines the effects of project-based learning and self-efficacy on prospective teachers’ mathematics pedagogical content knowledge. The study uses a quasi-experimental design, the experiment group learnt by project based learning and control group learnt by traditional method. Mathematics pedagogical content knowledge’s data collected using essay performance test and self-efficacy’s data collected by 5 points Likert scale. Results indicate PBL significantly boosts MPCK, especially for participants with high self-efficacy, underscoring self-efficacy’s key role in maximizing PBL’s effectiveness in teacher education.