Purpose: This paper aims to explore whether formal, non-formal, and informal learning experiences contribute to developing sustainable development competencies (SDCs) among students in a Principles of Responsible Management Education (PRME) signatory business school. Design/methodology/approach: An online survey based on the students' learning experiences and a questionnaire on sustainability competencies already validated in the literature were given to a sample of 274 bachelor students at a PRME signatory business school. Nominal variables representing students' categories were created to test a set of hypotheses developed according to the literature. Because the data was not normally distributed, non-parametric independent-samples Mann-Whitney U test was conducted, and descriptive statistics was used to help the analysis. Findings: The results suggest that a hybrid format with a combination of formal, non-formal and informal learning experiences is essential to maximising the development of SDCs and raising students' sustainability literacy. Research limitations/implications: This study is one of the first attempts to understand the importance of a hybrid approach in developing sustainable competencies (SDCs). Future studies could adopt longitudinal analysis to check the development of these competencies over time, assess students from different PRME signatory schools or comparing students to those in non-signatory business schools. Practical implications: This study provides insight into how business schools could address challenges in developing sustainable competencies through redirecting their educational systems by balancing formal, informal and non-formal learning approaches to educate future responsible leaders. Originality/value: This research provides evidence on how a hybrid learning approach could maximise the development of sustainable development competencies and, therefore, generating insights for educational policies.