A vehicle pedal assembly support structure comprises: a bracket to which a pivot shaft for a pedal lever is mounted; a guide member fixed to a vehicle body member other than a dash panel; a fixing mechanism for normally fixing a rear end portion of the bracket to a front end portion of the guide member but disengaging the bracket from the guide member in a vehicle collision; and a relative shift restricting member for restraining the rear end portion of the bracket from relatively shifting in directions other than the rearward direction of the vehicle to the front end portion of the guide member. The guide member is provided with a guide surface for downwardly guiding the bracket moving backward in the vehicle collision to change the posture of the bracket.