Affect dysregulation, defined as the impaired ability to regulate or tolerate negative emotional states, has been associated with interpersonal trauma and posttraumatic stress. Affect-regulation difficulties play a role in many psychiatric conditions, including anxiety and mood disorders, and especially major depression in youth and bipolar disorder throughout the life span. Exposure to traumatic events and interpersonal trauma in childhood is associated with wide-ranging psychosocial, developmental, and medical impairments in children, adolescents, and adults, with emotional dysregulation being a core feature that may help to account for this heightened risk. In order to understand how the developmental effects of childhood maltreatment contribute to emotional dysregulation and psychiatric sequelae, we review emotional regulation and its developmental neurobiology, and examine the research evidence of associations between childhood trauma, emotional dysregulation, and psychiatric comorbidities in children, adolescents, and adults.