An apparatus for mixing an exhaust gas stream with an additive, in particular a reducing agent. The apparatus has a mixing pipe for mixing the exhaust gas stream with the additive. The apparatus has a first deflection pipe for deflecting the exhaust gas stream, in particular by about 180°. The exhaust gas stream can be fed to the mixing pipe on the end side via the first deflection pipe. The first deflection pipe has a fastening region for attaching an additive injector to the first deflection pipe. The first deflection pipe has a swirl generating wall region arranged on the end side with respect to the mixing pipe and is configured to impart a swirl to the exhaust gas stream.