Insomnia is present in a majority of individuals with posttraumatic stress disorder (PTSD). However, when both disorders are present, disagreements exist about whether to provide exposure therapy for PTSD before insomnia treatment, or vice versa. The current case study describes the psychological treatment of a psychotherapy-naive veteran with comorbid insomnia and PTSD. The patient initially refused exposure therapy for PTSD; thus, cognitive-behavioral therapy for insomnia (CBTi) was a first-step treatment. Cognitive Behavior Therapy for Insomnia provided insomnia symptom relief psychoeducation and self-monitoring of PTSD symptoms prepared the patient to enter exposure therapy. After six CBTi sessions, the patient completed seven sessions of trauma-specific exposure therapy. At the conclusion of treatment and at 90-day follow up, the patient demonstrated significant reductions in insomnia and PTSD symptoms. Findings support the safe and effective use of CBTi in patients with comorbid insomnia and PTSD to improve sleep and facilitate entry into exposure therapy for PTSD.