This study investigates the effects of employees' positively oriented organizational behavior and organizational citizenship behavior (OCB) use on knowledge sharing behavior after a two-month period. Based on previous research, it was expected that: (1) organizational citizenship behavior would be positively related to knowledge sharing behavior; (2) psychological capital would be positively related to knowledge sharing behavior; (3) OCB would mediate the relationship between psychological capital and knowledge sharing behavior; (4) psychological empowerment would be positively related to knowledge sharing behavior; and (5) OCB would mediate the relationship between psychological empowerment and knowledge sharing behavior. Results provided support for the direct effects of OCB, psychological capital and psychological empowerment on knowledge sharing behavior. Psychological capital and psychological empowerment were each indirectly related to knowledge sharing behavior, mediate by OCB. To be more precise, individuals with higher level of psychological capital and psychological empowerment were not only more likely to participate in organizational citizenship behavior but having a higher level of positively orientated organizational behavior made them to engage more in knowledge sharing behavior two months later.