An internal combustion engine exhaust system mixer includes a mixer body (12) with deflection elements (16) extending radially outwards from a mixer body center (14). A ring-shaped carrier area (22) adjoins the mixer body radially on the outside and encloses a mixer longitudinal axis. The carrier area includes a mixer connection area (24) for connecting the mixer (10) to an exhaust system component. A pipe connection wall (30) adjoins the mixer connection area and has a wall inner surface (32). A mixer body carrier wall (34) adjoins the mixer connection area, carries the mixer body, and is enclosed by the pipe connection wall. A first transition surface (40) adjoins the wall and is arched essentially continuously concavely between the wall inner surface and the wall outer surface, and axially defines a ring-shaped pipe-mounting intermediate space (38) between the pipe connection wall and the mixer body carrier wall.