A brake actuating device of a motor vehicle brake system includes a master cylinder and a brake booster with a booster housing, with an attaching element for attaching the brake actuating device to a wall on the vehicle projecting through an opening from the booster housing. To improve the assembly, a means for the provisional attachment of the brake actuating device to the wall on the vehicle is provided, which cooperates in operative and/or positive engagement with the vehicle wall or a component that is arranged at the vehicle wall in an attached fashion.