An exhaust gas treatment device (1), for an exhaust system (1) of an internal combustion engine, includes a housing (2), providing an exhaust path (3), an injector (4) arranged on the housing (2) for introducing a reduction agent into an exhaust gas flow following the exhaust gas path (3), and a mixer (7) arranged in the housing (2). The mixer (7) includes a shell (8), which encloses a mixer cross section (10) through which the exhaust gas flow can flow. The mixer (7) includes multiple guide blades (11), which on a shell inside project from the shell (8) and project into the mixer cross section (10). A simplified producibility is obtained with the mixer (7) including multiple straps (13), on a shell outside (14), which project from the shell (8) and project into a strap opening (16) formed on the housing (2) and penetrate a housing wall (15).