A mixer for an exhaust system of an internal combustion engine includes a first mixer part (12) with a plate shape body (14) having an incoming upstream flow side (18), with respect to an exhaust gas main flow direction (A) and a downstream outflow side (22), and a second mixer part (24), on an outflow side, with a bottom wall (26) spaced apart from the plate shape body and with two side walls (28, 30), extending from the bottom wall (26) towards the plate shape body and fixed at the first mixer part. The mixer parts define a reactant injection duct (32) receiving reactant in a main injection direction (R). An exhaust gas main passage opening (54) the plate shape body opens towards the reactant injection duct with a plurality of exhaust gas secondary passage openings (78, 80, 82, 84, 86, 88, 90, 92) run past the injection duct.