Project-Based Learning (PBL) has emerged as a transformative instructional approach in Science, Technology, Engineering, and Mathematics (STEM) education. Unlike traditional teacher-centered methods, PBL emphasizes student-centered inquiry, real-world problem-solving, collaboration, and experiential learning. This study investigates the impact of Project-Based Learning on student engagement, critical thinking skills, problem-solving abilities, and academic achievement in STEM disciplines. A mixed-method research design involving 520 secondary and higher education students was employed. Data were collected through surveys, academic assessments, classroom observations, and interviews with educators. Findings reveal that PBL significantly enhances student motivation, collaboration, conceptual understanding, and STEM competency development. Students participating in project-based activities demonstrated higher academic performance and stronger problem-solving capabilities compared to those receiving conventional instruction. The study concludes that Project-Based Learning represents an effective pedagogical strategy for preparing students for twenty-first-century STEM careers and innovation-driven economies.