The invention relates to a method for monitoring a sensor unit (20) that is arranged in the exhaust gas region of an internal combustion engine (10). According to the invention, a sensor temperature (31, 32) is directly or indirectly determined by the sensor unit (20), and is compared to an exhaust temperature (33) that is determined by a further sensor unit and/or to model variables and/or to defined threshold values, whereby a dismounting and/or an inappropriate mounting of the sensor unit is indicated. The invention further relates to a device for monitoring a sensor unit (20) arranged in an exhaust region of an internal combustion engine (10), the sensor unit being used to directly or indirectly determine a sensor temperature (31, 32) which can be compared to an exhaust temperature (33) that is determined by a further sensor unit and/or to model variables and/or to defined threshold values in an engine control unit (14), wherein a malfunction entry and/or a warning signal can be derived from said comparison.