A vehicle seat having a backrest, which has a backrest middle part and backrest side parts, which extend forward laterally from the backrest middle part and are provided for lateral body support is described. The backrest side parts each have an internal section connected to the backrest middle part and an external section connected thereto, which overlaps a forward area of the backrest side part. The backrest side parts are adjustable in relation to the backrest middle part so that the backrest width is changeable by fixing the backrest side parts. The internal section and the external section are produced in one piece from a foam material. A stiffening element is foamed into the internal section and into the external section in a transition area between the internal section and the external section, which is primarily provided to give the external section a certain rigidity.