A control apparatus is disclosed for a diesel exhaust fluid injector located in an exhaust pipe of a diesel internal combustion engine. The control apparatus includes an electronic control unit configured to: energize a solenoid of the injector to perform a diesel exhaust fluid injection; determine an electric voltage value indicative of the electric voltage applied to the injector solenoid during the diesel exhaust fluid injection; determine an electric current value indicative of the electric current flowing through the injector solenoid during the diesel exhaust fluid injection; calculate an electric resistance value of the injector solenoid as a function of the determined electric voltage value and the electric current value; and estimate an injector temperature value as a function of the calculated electric resistance value.