Purpose: Service-learning (SL) shows potential to respond to the global policy agenda of education for sustainable development (ESD) by increasing pro-sustainability competences through direct involvement of students in projects that satisfy identified community needs. Nevertheless, there is a scarcity of studies that attempt to measure the impact of SL on students' sustainability competences, especially the action competence. This study aims to address this gap by examining the experiences of higher education students. Design/methodology/approach: A pre-post survey design based on the Self-Perceived Action Competence for Sustainability Questionnaire was conducted on an interdisciplinary group of 219 students of two courses (Sustainable Development and Ecology) in Medellin, Colombia, half of which (109) participated in SL projects. Findings: Sufficient empirical evidence was found to suggest that SL boosts the impact of academic courses regarding action competences in students (specially their willingness to act). Research limitations/implications: The statistical analysis shows some contradictions that should be addressed in further research. Practical implications: These results can encourage more educators and universities to implement strategies such as SL to move forward with ESD and thus help overcome the current socioecological crisis. Originality/value: This paper not only discusses the theoretical potential of SL but also contrasts theory with empirical observations of 13 SL projects assessed in terms of self-perceived action competence for sustainability.