Educators in the twenty-first century need to think of innovative ways to engage and prepare students for current and future challenges while cultivating an interest among students in STEM disciplines. This study sought to investigate the impact of problem-based learning on students' content knowledge and critical thinking towards STEM. This study employed a quasi-experimental repeated measure design. Instruments such as STEM content assessments and a standardized critical thinking test were employed for data collection. Analysis was conducted using a mixed repeated measure between-within subject analysis of variance (ANOVA). The results revealed a significant difference (p < 0.05) between problem-based learning and traditional learning groups in regard to their content knowledge and critical thinking skills.