The successful n‐type doping of CdTe and CdZnTe alloys by using iodine as a dopant is reported. For CdTe, doping levels as high as 6.2×1018 cm−3 can be obtained with carrier mobility around 500 cm2 V−1 s−1 at room temperature. An ionization energy of 14.8 meV has been determined for the shallow donor by Hall effect measurements. In the case of Cd1−xZnxTe ternary alloys, only a slight decrease in the carrier density is observed when increasing the Zn concentration, by contrast to doping with indium. The doping level of 5×1017 cm−3 can be achieved for a Zn concentration x as high as 0.25, demonstrating the higher efficiency of iodine doping as compared to indium doping.