This study examines how expectancy-value mediates the effects of sense of belonging and self-efficacy on academic performance among STEM students. Using a quantitative approach with a cross-sectional survey design, data were collected from 337 students at an Engineering School in Chile. Path analysis results indicate that self-efficacy and sense of belonging directly influence academic commitment, with expectancy-value acting as a significant but moderately impactful mediator. Notably, sense of belonging has a more substantial effect on academic commitment than self-efficacy, highlighting the importance of creating inclusive and supportive environments to enhance student retention in STEM. The practical implications suggest that strengthening self-efficacy and sense of belonging through pedagogical strategies such as collaborative learning and including mentors could be key to reducing dropout rates and increasing student success in these fields.