The invention relates to a heat exchanger (1), especially an exchanger for the air-conditioning system of a vehicle, allowing heat exchange between first (F1) and second (F2) fluids, said exchanger (1) comprising a plurality of tubes (3) for the circulation of the first fluid (F1), which are stacked one on top of the other, and at least one collector (5) comprising a collector plate (7), said collector plate (7) comprising openings (13) for inserting the ends (3a) of tubes (3), characterized in that said ends (3a) of said (3) are assembled at least two by two in the insertion openings of the collector plate (7).