The integration of STEM (Science, Technology, Engineering, and Mathematics) education is increasingly recognized for its potential to enhance problem-solving skills among K-12 students. This meta-analysis synthesizes findings from 18 diverse studies—spanning qualitative, quantitative, and mixed-methods approaches and various national contexts—to evaluate the effectiveness of STEM education in improving these critical skills. The studies, covering periods before, during, and after the COVID-19 pandemic, consistently affirm the positive impact of STEM pedagogy on students' problem-solving abilities. Additionally, this research explores the specific role of project-based learning (PBL) within STEM education, aiming to determine how much this teaching strategy can further augment students' problem-solving competencies. The results highlight the significant benefits of employing STEM strategies in general classroom settings and within PBL contexts in fostering enhanced problem-solving and critical thinking skills among K-12 students. This study contributes to the ongoing discourse on educational strategies, underscoring the value of STEM education in preparing students to tackle complex problems effectively.