To provide a brake control system capable of executing appropriate intervention braking.

The brake control system includes a collision predicting time calculating means for calculating collision predicting time required until a vehicle and an obstacle around the vehicle collide, a second intervention braking means for starting automatic intervention braking by a service brake when the collision predicting time becomes less than or equal to a predetermined service brake operation threshold value, a first intervention braking means for starting intervention braking by a retarder brake when the collision predicting time becomes less than or equal to a retarder braking operation threshold value longer than the service brake operation threshold value, an avoidance operation determining means for determining whether a collision avoidance operation for avoiding a collision by a driver of the vehicle has been executed during operation of the retarder braking by the retarder braking operation means, and a timing changing means for making a start timing of the automatic intervention braking by the second intervention braking means quicker than usual when the collision avoidance operation is determined not to be executed.