Module for mixing flows of two gases (G, H) for an internal combustion engine heat exchanger, the heat exchanger being intended to exchange heat with a first flow of gas, the module comprising: - a plurality of first strata for conducting the first flow of gas and - a plurality of second strata for diffusing a second flow of gas, the module comprising: - means for dividing the first flow of gas into a plurality of elementary flows of first gas (g1, g2,..., gn); - means of introducing the second flow of gas into the said mixing module, and - means for dividing the second flow of gas outside the mixing module into a plurality of elementary flows of second gas (h1, h2,..., hn), the elementary flows of first gas (G, H,..., gn) mixing with the elementary flows of second gas (h1, h2,..., hn), the means for dividing the first flow of gas comprising a plurality of mutually parallel separating leaves the said separating leaves being hollow and connected by one of their ends to the means for introducing the second flow of gas, the said module being characterized in that it comprises a substantially rectangular support frame in which the following are supported: - the separating leaves, and - retaining separators arranged to keep the separating leaves parallel to one another, the retaining separators being orthogonal to the separating leaves - and in which the introducing means take the form of a tubular duct forming one lateral edge of the rectangle representing the shape of the support frame. - a plurality of first strata for conducting the first flow of gas and - a plurality of second strata for diffusing a second flow of gas, the module comprising: - means for dividing the first flow of gas into a plurality of elementary flows of first gas (g1, g2,..., gn); - means of introducing the second flow of gas into the said mixing module, and - means for dividing the second flow of gas outside the mixing module into a plurality of elementary flows of second gas (h1, h2,..., hn), the elementary flows of first gas (G, H,..., gn) mixing with the elementary flows of second gas (h1, h2,..., hn), the means for dividing the first flow of gas comprising a plurality of mutually parallel separating leaves the said separating leaves being hollow and connected by one of their ends to the means for introducing the second flow of gas, the said module being characterized in that it comprises a substantially rectangular support frame in which the following are supported: - the separating leaves, and - retaining separators arranged to keep the separating leaves parallel to one another, the retaining separators being orthogonal to the separating leaves - and in which the introducing means take the form of a tubular duct forming one lateral edge of the rectangle representing the shape of the support frame. - means for dividing the first flow of gas into a plurality of elementary flows of first gas (g1, g2,..., gn); - means of introducing the second flow of gas into the said mixing module, and - means for dividing the second flow of gas outside the mixing module into a plurality of elementary flows of second gas (h1, h2,..., hn), the elementary flows of first gas (G, H,..., gn) mixing with the elementary flows of second gas (h1, h2,..., hn), the means for dividing the first flow of gas comprising a plurality of mutually parallel separating leaves the said separating leaves being hollow and connected by one of their ends to the means for introducing the second flow of gas, the said module being characterized in that it comprises a substantially rectangular support frame in which the following are supported: - the separating leaves, and - retaining separators arranged to keep the separating leaves parallel to one another, the retaining separators being orthogonal to the separating leaves - and in which the introducing means take the form of a tubular duct forming one lateral edge of the rectangle representing the shape of the support frame.