As part of the SuProm Project — Sustainable PRoject Management in Balkan Higher Education Institutions (Programme: EACEA - Erasmus+, KA2 - Capacity Building in the Field of Higher Education) — a study was conducted to evaluate the effectiveness of a two-day intensive training programme for university staff, researchers, and students. The intervention aimed to promote sustainability-oriented attitudes, self-efficacy, and behaviors in the field of project management. Thirty participants (N = 30) completed questionnaires administered at four time points: pre-intervention, during the intervention, post-intervention, and at a four-week follow-up. The measures included self-report scales assessing attitudes toward sustainability, perceived organizational support, environmental self-efficacy, social norm perceptions, and behavioral intentions. Qualitative data were also collected through open-ended questions. Quantitative analyses were conducted using repeated-measures and longitudinal mixed models, and the mediation hypothesis was tested via bootstrap procedures. The results revealed significant increases in self-efficacy for sustainable design and pro-sustainability intentions from pre- to post-intervention, with partial maintenance at follow-up. Mediation analysis indicated that increases in self-efficacy mediated the relationship between the intervention and reported behaviors. Thematic analysis of open-ended responses identified recurrent organizational barriers (e.g., resource constraints and time pressures) and produced operational recommendations for improving training programme implementation. Theoretical and practical implications for occupational and sustainability psychology, study limitations (e.g., sample size and reliance on self-report measures), and directions for future research are discussed.