To evaluate the effects of national training in and implementation of Cognitive Behavioral Therapy for Insomnia (CBT-I) in the U.S. Department of Veterans Affairs (VA) health care system on clinicians' competency and patients' insomnia severity, symptoms of depression, and quality of life. A prospective cohort of 102 VA clinicians (including mental health staff in various mental health and primary care settings) participated in the VA CBT-I Training Program during 2011 and 2012. Patients included 182 veterans treated by clinicians enrolled in the training. Clinicians were rated on taped therapy sessions, using a standardized competency rating form. Patients' symptoms were assessed using the Insomnia Severity Index (ISI) and standardized measures of depression and quality of life. Of 102 clinicians attending workshop training, 94 (92%) met all training requirements, including minimum competency score criteria. Of 182 patients, 122 (67%) completed treatment. The mixed effects model revealed significant reductions in average patient ISI score (from 19.9 to 10.2, standard error = 3.0). Patients also improved on measures of depression and quality of life. National training in and implementation of CBT-I resulted in a significant increase in therapist competency to deliver CBT-I for almost all clinicians and in a large reduction in insomnia severity and improvement in depression and quality of life among veterans. Observed effect sizes are comparable to results of randomized clinical trials. These results suggest CBT-I can be feasibly and effectively disseminated to routine clinical settings, with very favorable patient outcomes.