A bumper beam assembly for a vehicle may include a back beam disposed inside a vehicle bumper, both distal ends of the back beam being oriented in a lateral direction of a main body of the vehicle, crash boxes coupled to one side of the back beam, the crash boxes protruding from the both distal ends of the back beam toward the bumper, and back beam stays integrally coupled to the other side of the back beam, the back beam stays protruding from the both distal ends of the back beam toward an inside of the vehicle, in a direction opposite to a direction in which the crash boxes protrude.