Imagery rehearsal therapy (IRT) may help reduce residual nightmares and posttraumatic stress disorder (PTSD) symptoms in veterans after trauma-focused PTSD treatment. Fifteen male U.S. veterans with PTSD and trauma-related nightmares, who had not previously completed trauma-focused PTSD treatment, attended 6 IRT group sessions. No benefits were observed immediately posttreatment. At 3- and 6-month follow-up, however, trauma-related nightmare frequency (nights/week) decreased (p < .01). The number of trauma-related nightmares/week (p < .01), number of total nightmares/week (p < .05), and PTSD symptoms (p < .05) also decreased at 3 months. The overall F test for time was significant (p < .05) for nightmare severity and fear of sleep. No effects were found on measures of the impact of nightmares, sleep quality, or depression. Clinical and research implications are discussed.