This was an observational study of 74 veterans of Operation Iraqi Freedom/Operation Enduring Freedom (OIF/OEF) who reported histories of exposures to explosions that produced mild traumatic brain injury (TBI), also called concussion. Each of these OIF/OEF veterans had headaches, and each had abnormal findings on neurological examination, performance deficits on neuropsychological testing, or both. They also had a high frequency of posttraumatic stress disorder (PTSD) and impaired sleep associated with nightmares. At baseline, they were having, on average, more than 12 headaches a month, peak headache pain of 7.28 on a 0 to 10 scale, increased daytime sleepiness (determined by the Epworth Sleepiness Scale [ESS]), and mild cognitive impairment on the Montreal Cognitive Assessment (MOCA). The veterans received sleep hygiene counseling and oral prazosin at bedtime. At the end of a 9-week intervention period, the 62 veterans who took prazosin had reduced headache pain and frequency and improved MOCA and ESS scores. We evaluated the veterans again at the end of a 6-month follow-up period, and the 64 veterans who were using prazosin showed further reduced headache pain and frequency and improved ESS scores. We believe that prazosin combined with sleep hygiene counseling is an effective initial intervention for veterans with mild TBI who have headaches and impaired sleep associated with PTSD. We suggest that sleep hygiene counseling may help veterans fall asleep and that prazosin prevents sleep interruptions by blocking nightmares. Improvement in sleep may contribute to improved cognitive function, headache control, and reduced daytime sleepiness.