Radiotherapy-induced alopecia (RIA) is characterized by an acute anagen effluvium (AE) caused by intense damage to the hair follicle. It may be temporary or permanent, depending on the radiation dose. The diagnosis is based on clinical history and dermatologic exam with trichoscopy being auxiliary the presence of flame hair. The presence of flame hairs (FHs) is a valuable finding in the diagnosis of anagen effluvium (AE) secondary to radiotherapy. FH is the most characteristic conformation observed in the trichoscopy of AE. We present a case of AE induced by radiotherapy emphasizing the trichoscopic findings and the most relevant clinical aspects in this type of alopecia.