The study examined the impact of contingent employment on organizational citizenship behaviour. Seven hundred and fifteen (715) participants, drawn from a commercial bank and an oil company in southwest, Nigeria, participated in the study. Organizational citizenship behaviour (OCB) was assessed with a 21-item questionnaire reflecting two dimensions of citizenship behaviour; OCB directed at specific individuals in the organization (OCBI) and the one directed at the organization (OCBO). The results showed that employees in permanent employment exhibited higher citizenship behaviour than those in contract employment: F = 29.13, df = 1, 713, p < .001. The results were interpreted in relation to partial inclusion model and the findings were also discussed based on Nigerian socio-economic realities. The findings have implications for organizational researchers and practitioners who are seeking to improve organizational effectiveness through contingent employment and other alternative work arrangements.