A 15-year-old girl developed a prominent delayed sleep phase syndrome (DSPS) following traumatic brain injury. Several physiological markers of the sleep-wake rhythm: plasma melatonin, body temperature, wrist activity and sleep architecture (EEG) were delayed almost half a day, returning to normal after treatment with 5 mg melatonin. This report suggests an association between traumatic brain injury and DSPS. Awareness of this phenomenon may result in better possibilities for treatment of patients with brain injury.