Heat exchanger for exchanging heat between at least two fluids which are guided through chambers of the heat exchanger (1), wherein at least one guiding profile (11) is provided in the chambers (19,20), and the guiding profile (11) is an extruded tubular profile (12) which includes two parallel walls (13) which are connected to one another by means of two sidewalls (14). One or several dividing walls (15) extend in the extrusion direction of the tubular profile (12). One or several passages (17) are provided in the dividing walls (15) and/or in the sidewalls (14) for guiding a fluid.