Purpose: Pro-environmental education incorporates digital technologies to enhance the level of pro-environmental behaviours (PEB) in young adults. Guided by gamified learning and self-directed informal learning theories, this study aims to examine the potential for the use of a gamified mobile app to increase students' PEB. Also, it explores whether various pre-existing environmental attitudes and beliefs can moderate the effects. Design/methodology/approach: This quasi-experimental study proposed an eight-weeks intervention for undergraduate students based on using a mobile app. The authors evaluated the post-intervention differences in PEB between the intervention group and a control group. The effects of multiple moderators were also tested. Findings: Using the mobile app for eight weeks significantly improves the levels of PEB in the intervention group compared to the control group. None of the proposed interactions showed significant moderator effects. Originality/value: To the best of the authors' knowledge, this study is the first one to verify the potential moderators accounting for the success of an environmental education approach using a mobile app. Also, it provides strong empirical support for the use of such educational strategy. Based on these findings, the authors suggest the use of gamified mobile apps as suitable tools for pro-environmental education, especially when targeting young adult or student populations. Moreover, using mobile apps providing self-directed informal learning, combined with gamification, can be used to enhance other desirable behaviours.