Introduction: Smartphone addiction among adolescents has become a growing public health concern due to its association with poor academic performance, sleep disturbances, and mental health problems. This study applied the Health Promotion Model (HPM) and Self-Determination Theory (SDT) to identify cognitive and motivational factors associated with adolescents’ commitment to preventing smartphone addiction. Methods: A cross-sectional study was conducted among 307 senior high school students from five public schools in Malang City, Indonesia, selected using cluster random sampling. Data were collected through validated questionnaires adapted from the HPM framework, the Basic Psychological Needs Scale, and the Smartphone Addiction Scale–Short Version. Structural Equation Modeling (SEM) using SmartPLS was employed to examine the relationships among perceived barriers, self-efficacy, competence, autonomy, relatedness, and commitment to prevent smartphone addiction. Results: Competence was the strongest positive predictor of commitment to prevent smartphone addiction (β = 0.488, p < 0.001), followed by relatedness (β = 0.213, p < 0.001). Self-efficacy showed a significant negative association with commitment (β = −0.124, p = 0.020). In contrast, autonomy (β = 0.016, p > 0.05) and perceived barriers (β = −0.047, p > 0.05) were not significant predictors. The measurement model demonstrated satisfactory validity and reliability, while the structural model showed acceptable fit (SRMR = 0.069) and explained 45.2% of the variance in commitment (R² = 0.452). Conclusion: Competence, relatedness, and self-efficacy significantly influence adolescents’ commitment to preventing smartphone addiction. Strengthening psychological competence, social connectedness, and self-regulatory capacities may enhance the effectiveness of school-based smartphone addiction prevention programs.