Background <p>Academic burnout (ABO) poses a significant threat to student well-being and performance, particularly among premedical undergraduates. While informal peer-assisted learning (IPAL) may mitigate this burden, limited research has explored this relationship in nonmedical student populations. The objectives of this study are to assess the psychometric validity of the SBI-9 in the undergraduate population and to investigate whether a relationship exists between ABO and IPAL in this population.</p> Methods <p>We conducted a cross-sectional survey of 245 undergraduate students at the University of Puerto Rico, Río Piedras Campus. ABO was measured using the nine-item School Burnout Inventory (SBI-9). IPAL engagement was assessed through a single-item measure. Internal consistency, item correlations, and confirmatory factor analysis (CFA) were performed to validate the SBI-9. ABO levels were analyzed by age, gender, academic year, study preference, and IPAL engagement.</p> Results <p>The SBI-9 demonstrated high internal consistency (Cronbach’s α = 0.872) and a validated three-factor structure. Overall, ABO levels increased slightly across academic years, with the highest scores observed in fifth-year students. Female students reported significantly higher ABO than males, particularly in the first two years. Globally, students who never engaged in IPAL reported significantly higher ABO scores (mean = 48.41) compared to those with occasional or frequent IPAL engagement (mean = 42.48, <i>p</i> = 0.0384). A similar trend was observed in students who preferred studying alone.</p> Conclusions <p>Informal peer-assisted learning may serve as a protective factor against academic burnout among undergraduate students. Gender differences and study habits further influence ABO vulnerability. Early peer-based interventions may promote academic resilience and psychological well-being in premedical populations.</p>