This study investigates the influence of newcomers’ personality on their psychological contract. Especially, we focused on the proactive personality of the newcomers who have worked less than one-year in the current organization. We hypothesized that the extent to which newcomers have proactive personality would have a positive effect on the perception of promise in the relationship with the organization. Also, we expected that this relationship would be mediated by the leader-member exchange. 433 newcomers participated in the survey, and structural equation modeling (SEM) has been adopted to test the hypotheses. As the result, individuals’ proactive personality had a positive influence on the perception of promises, and this relationship was partially mediated by the leader-member exchange level. These results imply that individuals’ psychological contract could be affected by personality factors as well as organizational factors. Also, it shows that the relationship newcomers make with their supervisor has an important role in perceiving psychological contract with the organization.