A method is provided for the decontamination of radioactive carbonaceous material, such as graphite, in which an injection of steam is planned into the material, concurrent with a first roasting thermal treatment of the material at a temperature between 1200° C. and 1500° C. Advantageously, the first treatment may be followed by a second treatment at a lower temperature with an injection of carbon oxide for oxidation according to the Boudouard reaction.