This study theoretically examines and empirically tests factors expected to affect an individual’s knowledge sharing attitudes, intention and behavior in an organizational context. The research model is constructed based on the economic exchange theory, the social exchange theory, the self-efficacy theory and the theory of reasoned action. Results from the field survey of 467 employees of four large and government-invested organizations show that ‘anticipated reciprocal relationships’ and ‘perceived personal contribution to the organization’ are the major determinants of the individual’s attitudes towards knowledge sharing. ‘Anticipated extrinsic rewards,’ believed by many as the most important motivating factor for knowledge sharing, are not significantly related to the attitudes towards knowledge sharing. As expected, positive attitudes towards knowledge sharing are found to lead to a positive intention to share knowledge and, finally, to actual knowledge sharing behaviors.