The invention relates to a collection box (1) for a heat exchanger comprising a collector (5) having an at least partially rounded shape and including: a plurality of openings (7) for passing a plurality of heat-exchange tubes (3) of the heat exchanger, and a plurality of collars (9) surrounding the openings (7). According to the invention, the collector (5) comprises a plurality of corrugations (11), and the collars (9) are formed at the corrugations (11) of the collector (5) and have a substantially flared shape, respectively, in the direction of the side opposite the space defined by the collection box (1).