A heat exchanger for cooling motor vehicle exhaust gases, which heat exchanger is to be fitted into an exhaust line of the vehicle and having at least three tubes in contact by way of their outer walls with cooling air, in which the exhaust gases are brought to circulate. The exchanger has an outer casing of sheet metal that is substantially cylindrical in shape and through the lateral wall of which there pass openings, in which casing the tubes are fixed by holding means in substantially parallel arrangements inside the casing, a pipe for the admission of exhaust gases into the casing of the heat exchanger which pipe is connected to the exhaust line upstream of the heat exchanger, an exhaust gas evacuation pipe connected to the exhaust line downstream of the heat exchanger, and exhaust gas distribution means arranged inside the casing of the heat exchanger, the exhaust gas distribution means allowing the exhaust gases to be passed from the admission pipe to the evacuation pipe along a path that passes in succession, in an axial direction, through each of the tubes of the plurality of tubes along their entire length. There are also at least four collectors delimited, inside the metal casing of the heat exchanger by two axial-end cupels or outer cupels that are arranged transversely and close the axial ends of the metal casing of the heat exchanger.