The invention relates to a heat exchanger for an EGR (Exhaust Gas Recirculation) system, comprising a tube bundle of flat tubes, configured by combining two plates incorporating specific protrusions distributed according to the direction of the tube. These protrusions in both plates are in contact with one another or attached such that they establish internal channels. The present invention is characterized by the presence of either transverse projections or of transverse deviations generating disturbances in the flow through side walls of the internal channels, increasing the turbulence of the flow through said channels and thereby increasing heat exchange by convection.