Purpose This study aims to examine the influence of employee vitality and tenure on the nexus between citizenship fatigue and knowledge-sharing behaviour among academic staff in Ghanaian higher education institutions. Design/methodology/approach A sample of 876 faculty members from traditional and technical universities was chosen for the study using convenience sampling technique. Data was analysed using PLS-SEM with SmartPLS 4. Findings Results reveal that citizenship fatigue negatively influences faculty members’ knowledge-sharing behaviour. In addition, employee vitality and tenure mitigate the negative influence of citizenship fatigue on faculty members’ knowledge-sharing behaviour. Practical implications The findings suggest that the management of higher education institutions should focus on creating a workplace culture that cultivates workplace vitality and promotes long tenure to reduce the negative influence of citizenship fatigue on the knowledge-sharing behaviour among faculty members. Originality/value This study represents one of the earliest attempts to examine a theoretical framework that connects citizenship fatigue, employee vitality, knowledge-sharing behaviour and employee tenure within the context of higher education.