Disorders of diminished motivation occur frequently in individuals with traumatic brain injury. Motivation is an ever-present, essential determinant of behavior and adaptation. The major syndromes of diminished motivation are apathy, abulia, and akinetic mutism. Depending on their etiology, disorders of diminished motivation may be a primary clinical disturbance, a symptom of another disorder, or a coexisting second disorder. This article presents a biopsychosocial approach to the assessment and management of motivational impairments in patients with traumatic brain injury. The recognition and differential diagnosis of disorders of diminished motivation, as well as the mechanism and clinical pathogenesis, are discussed.