An injection device (14), for introducing a reducing agent (11) into an exhaust gas stream (8) of an exhaust system (7) of an internal combustion engine (1), has an exhaust pipe (15) for guiding the exhaust gas stream (8), which has a connecting piece opening (18) in a wall (17). A connecting piece (16) is inserted with an inner end (19) into the connecting piece opening (18) and is provided for connecting an injector (10) at an outer end (20). Simplified assembly is achieved if the connecting piece (16) has, at an inner end (19), a laterally projecting, fully circumferentially extending collar (22). The collar (22) is in contact, on an inner side (23) of the wall (17), with an opening edge (24) enclosing the connecting piece opening (18) and is welded to the wall (17).