A vehicle body structure has a first structural member that at least partially defines an upper side of a door opening and a second structural member that extends downward from the first structural member and at least partially defines one side of the door opening. An elongated track member is attached on the first structural member. A sliding door is movably supported on the track member for movement along the track member between a closed position and an open position. A stopper bracket is rigidly attached on the second structural member. The stopper bracket is dimensioned and configured to absorb impacting forces of the sliding door as the sliding door moves from the closed position to the open position. The stopper bracket is rigidly attached to the track member such that the impacting forces are at least partially transmitted to the track member.