Purpose – Universities may display strong sustainability identities without embedding environmental priorities in their employment systems. This study examines whether Universitas Palangka Raya’s (UPR) public sustainability signals are reflected in employee-perceived Green HRM system strength, green psychological climate, and organisational citizenship behaviour for the environment (OCBE). Design/methodology/approach – A sequential single-case design combined a structured audit of 29 official documents from 11 UPR units with a cross-sectional employee survey (n = 250). The survey model was estimated using PLS-SEM, representing system strength through distinctiveness, consistency, and consensus, green psychological climate as mediator, and OCBE through eco-civic engagement, eco-helping, and eco-initiatives. Finding/Results – The audit identified strong environmental knowledge, infrastructure, and stakeholder engagement but weak public codification of recruitment, appraisal, and reward practices. System strength was positively associated with green psychological climate (β = 0.556, p < .001) and OCBE (β = 0.220, p < .001), while green psychological climate was positively associated with OCBE (β = 0.439, p < .001). The indirect effect was significant (β = 0.244, p < .001), indicating complementary partial mediation. Originality/Value – The study connects institution-level digital evidence with employee-level process perceptions in a single higher-education case. UPR can strengthen its system by formalising green competencies, development, role-relevant performance criteria, recognition, and transparent communication.