A heat exchanger is provided for an exhaust system of an internal combustion engine. The exchanger has a thermoelectric generator which comprises a hot side and a cold side with a heating pipe arranged on one hot side of the thermoelectric generator, and with a cooling pipe arranged on one cold side of the thermoelectric generator. The thermoelectric generator the heating pipe, and the cooling pipe are stacked in a stack direction on top of one another and form a pipe stack, in which the respective thermoelectric generator, heating pipe and cold pipe extend parallel to one another in a longitudinal direction of the pipe stack. An increased energetic efficiency is obtained. A heat transfer structure has a heat transfer capability favoring a heat transfer between the respective pipe and the respective media conducted therein.