This study analyzes how service-learning contributes to the level of commitment to environmental sustainability in higher education institutions (HEIs), as perceived by their students. The empirical analysis has been conducted by using the PLS-SEM modelling, on a sample of 366 undergraduate students of business from Croatia and Bosnia & Herzegovina. The obtained results support the hypothesized influence of the service-learning development level on the sustainability commitment in higher education. We also consider the indirect effects within the model. They show that service-learning mediates the relationships between students’ idealism and sustainability commitment, as well as between students’ social trust and sustainability commitment. Implications of obtained empirical results for theory and higher education practice are discussed. The potential for generalizing results for other sustainability interventions is assessed.