Research on Organizational Citizenship Behaviour (OCB) in the workplace is increasingly gaining momentum. The broad objective of the present study was to examine the nature of OCB and its dimensions in the private and public sector Indian organizations and also to investigate the relationship that OCB bears with sources of work motivation. The sample consisted of 400 workers drawn equiproportionately from the private and public sector organizations located in three districts of West Bengal. Data were collected by the administration of an OCB Scale developed by the present researcher in consultation with the conceptual framework of Organ, Podsakoff, Pattanayak and an adapted version of Motivation Sources Inventory. The standard item analysis technique was followed to develop the OCB scale and simple correlation was also done to understand the relationship of OCB with that of motivational sources in the private and public sectors. Besides, the comparison of both the sectors with respect to OCB and Work Motivation was done by applying t-tests on the present sample. The results indicated the emergence of three new factors with respect to the conceptualization of OCB. It was also revealed that OCB (on its seven dimensions and as a global measure) tended to be higher in private sector workers than that of the public sector workers. Work Motivation with respect to the workers of the two sectors presented a mixed picture, with "t" differences being significant on three sources and insignificant on the other two. The relationship of OCB with that of Work Motivation, as depicted, by the correlational analysis, is significant in private sector organizations whereas the same relationship is insignificant in the public sector organizations. Thus, it may be concluded that focusing on OCB could positively set new trends and vistas in how the private and public sector organizations may utilize the capacity of their workers in transforming the organizations into true 'performing' ones. © Journal of the Indian Academy of Applied Psychology.