In higher education, equipping students with the competences to navigate complex sustainability challenges is increasingly critical. This study investigates the impact of the “Circular Spring” – a project-based initiative held at the University of Naples Parthenope, which integrates interdisciplinary seminars with a student-led circular economy (CE) contest. The study examines how experiential learning fosters sustainability-related competences defined in UNESCO's Education for Sustainable Development (ESD) framework and transformative capacities framed by the Inner Development Goals (IDGs). Results indicate that participants show significant gains in cognitive, socio-emotional, and behavioral dimensions, including systems thinking, critical reflection, collaboration, self-awareness, empathy, and resilience, which can be mapped onto key ESD competence domains and IDG dimensions such as Being, Relating and Acting. These findings provide empirical evidence that experiential programs can support the joint development of sustainability competences and IDG-related inner capacities and offer a structured lens for assessing how higher education initiatives contribute to holistic sustainability learning and the design of circular economy education.