This article examines the mediating role of public service motivation (PSM) on the relationship between employees’ perceptions of corporate social responsibility (CSR) and organizational citizenship behavior (OCB). A sample of employees working in public sector banks in Egypt completed a structured questionnaire comprising of questions regarding CSR perceptions and PSM. Immediate supervisors rated the OCB of employees who responded to the survey. Results reported in the paper found the following: a) Employee perceptions of both internal and external CSR had a positive influence on the development of employee desire to serve the public; b) PSM partially mediated the relationship between internal CSR perceptions and employee OCB; c) PSM fully mediated the relationship between external CSR perceptions and OCB. This study extends current knowledge of the theoretical foundations surrounding CSR at the individual-level of analysis and offers practical implications by stressing the importance of employee desire to serve the public.