This study examines the relationship between corporate volunteerism and organizational citizenship behavior(OCB), considering employees` personal values. It is assumed that corporate volunteerism based on intrinsic motives of employees positively relates with OCB orientation, which is a indicator of organizational effectiveness. This study surveyed 2,315 employees out of 31 Korean companies and analyzed these collected data to test our hypotheses. The results reveal that employees` personal values associate with intrinsic motives of participation in volunteer activities, and their volunteerism carried out by intrinsic motives positively correlates with their OCB orientation. In conclusion, this study implies that corporate volunteerism, by improving OCB, can contribute to not only organizational effectiveness, but also social welfare. In addition, it can develop more harmonious relationship between the company and society.