Nightmares are often a distressing symptom for veterans with chronic combat-related posttraumatic stress disorder (PTSD). A psychological treatment that has recently shown considerable promise is Imagery Rehearsal Therapy (IRT). In a pilot study by the current authors, IRT was demonstrated to be effective in the treatment of posttraumatic nightmares in a group of combat veterans up to 3-month posttreatment. This study reports the 12-month follow-up data of the pilot study, examining the longer term outcome of the IRT treatment. Twelve Australian Vietnam veterans with chronic combat-related PTSD were treated with 6 once weekly sessions of imagery rehearsal and assessed using standardised measures of nightmare frequency and intensity, PTSD, depression, anxiety and broader symptomatology at intake, posttreatment, and 3-and 12-month follow-up. Significant improvements in targeted nightmare frequency and intensity were evident to 12-month posttreatment. Similarly, improvements in overall PTSD, depression, anxiety, and broader based symptomatology were also maintained to 12 months. This study provides preliminary evidence that the positive treatment effects of IRT on posttraumatic nightmares, PTSD, and broader symptomatology in males with chronic combat-related PTSD are maintained in the longer term.