From a relational perspective, this study suggests new types of knowledge transfer based on the tenure difference between a knowledge source and a recipient, and explores different motivational mechanism for each type of knowledge transfer. This approach is different from previous ones treating a tenure difference as a cognitive difference that prohibits knowledge transfer. The research model based on the theory of planned behavior was verified using structural equation modeling. The results show that self-efficacy is the strongest antecedent of downward knowledge transfer. On the other hand, in upward knowledge transfer, subjective norm is the most influential. Lastly, in lateral knowledge transfer, expected reciprocity shows a significant effect, but in the negative direction. These results validate the usefulness of the relational approach in understanding the motivational mechanisms of knowledge transfer.