Disclosed herein is an over-slam bumper for a vehicle. The over-slam bumper includes: a bumper unit (100) of which an end portion protrudes toward a door to absorb shock generated between a vehicle body and the door; and a mounting unit (200) coupled with the bumper unit (100) to fix the bumper unit to the vehicle body, wherein the bumper unit (100) includes: an elastic part for absorbing shock generated when getting in contact with the door; and a coupling part (116) connected to the elastic part and coupled with the mounting unit (200). The elastic part includes a buckling part (111) for absorbing shock by buckling; a compression part (130) for absorbing shock by compression; and an elastic air compression part for absorbing shock by sealing the inside air to compress inside air.