A vaporizer for an exhaust system of an internal combustion engine has a vaporizer tube and a holding sleeve in which the vaporizer tube is inserted. A clamping sleeve sits on the vaporizer tube. The vaporizer tube includes two circumferentially surrounding clamping surfaces which protrude in a radial direction and cooperate with the holding sleeve and the clamping sleeve such that the clamping surfaces are clamped between the holding sleeve and the clamping sleeve by an axial clamping force to be gastight. At least one of the holding sleeve and the clamping sleeve includes a surrounding sealing edge which rests against the respective clamping surface via a line contact and forms an annular sealing seat. The vaporizer further includes a device preventing relative rotation between the holding sleeve and the vaporizer tube. A heater of the vaporizer is attached to the vaporizer tube using a resistance welding method.