This study examines the impact of occupational self-efficacy on organisational citizenship behaviour (OCB) in West Bengal's healthcare sector, with employee engagement as a mediating factor. Data were collected using a structured questionnaire, analysed via SPSS AMOS, SPSS, and MS Excel. Confirmatory factor analysis (CFA) assessed model fit, followed by linear regression and bootstrapping approach for mediation analysis. Occupational self-efficacy significantly influences OCB, with employee engagement mediating this relationship. This study uniquely explores a broad range of healthcare employees in West Bengal, linking the findings to social exchange and self-efficacy theories. The study highlights the critical role of employee engagement in enhancing OCB. HR departments and administrators should focus on fostering engagement, organisational commitment, and job satisfaction to improve OCB.