Abstract: A heat exchanger for an exhaust gas recirculation system includes an exchanger body delimiting an inner volume, and longitudinal tubes housed in the inner volume and forming a layer of tubes fitting between upper and lower planes. The tubes are separated by passages for circulating a second fluid, the upper plane being across from an upper part of the exchanger body. A second fluid inlet is arranged in the upper part of the exchanger body; and a member guides the second fluid in the inner volume. A deflector at least partially closes off the interstitial space between the upper part and the upper plane.