ENPurpose – The purpose of this paper is to examine the role of prosocial and intrinsic motivation and their interaction in predicting employees’ organizational citizenship behaviour (OCB) and its dimensions. Design/methodology/approach – In total, 884 employees from Lithuanian public sector were surveyed. The hypotheses were tested using hierarchical regression and moderation analyses. Findings – The results revealed that prosocial and intrinsic motivations predicted OCB and its dimensions. Moreover, intrinsic motivation was found to moderate the relationship between prosocial motivation and OCB and four of its dimensions, i.e. intrinsic motivation strengthened the relationship between prosocial motivation and OCB and its dimensions of altruism, courtesy, conscientiousness, and initiative. Research limitations/implications – The correlational design of the study does not allow making causal statements. In addition, the sample consisted of public sector employees only; therefore, caution should be made when applying the results to private sector employees. Finally, since all measures were self-reported, the data may suffer from common method bias. Originality/value – This study contributes to investigation of motivational antecedents of OCB by revealing the importance of prosocial and intrinsic motivation in predicting employees’ citizenship behaviour. [From the publication]