Cerebral cavernomas are thin-walled vascular lesions composed of dilated capillary spaces. De novo formation of cavernomas after cerebral radiotherapy has been suspected since 1994. They are mostly seen in children after irradiation of brain tumours. Radiation dose and the developing juvenile brain are predisposing factors causing cavernomas. However, the underlying mechanisms are still far from being understood. In adults, radiation-induced cavernomas (RICs) usually occur 10 years after a high cumulative radiation dosage of >30 Gy. Here, we report a 45-year-old man with new-onset focal epileptic seizures caused by a haemorrhagic lesion noted on cerebral computed tomography scan. Brain MRI showed the typical appearance of a ruptured cavernoma. Of note, a cerebral MRI scan 5 years earlier showed no corresponding lesion. The patient had been treated with haematopoietic stem cell transplantation for acute myeloid leukaemia (AML) 16 years before. As part of this procedure, total body irradiation (TBI) consisting of 12 Gy was administered. According to the data from the literature, the typical delay from irradiation and a former normal brain MRI scan, we assume that our patient suffers from a RIC. To our knowledge, this is the first documented adult AML patient with a RIC treated with TBI. We aim to increase awareness among neurologists for the association of cranial irradiation or TBI and de novo cavernomas in patients suffering from malignant diseases.