Lasting emotional and social communication deficits are common among children who have suffered brain injury. Concerns have been raised that current assessment and treatment methods are inadequate in addressing the needs of such children in rehabilitation. We advocate that a proportion of reported deficits occur as a result of compromise to emotion processing systems in the brain. In this article we review adult brain injury research, which indicates that dissociable subsystems are involved in distinguishing the nuances of emotional expression. Findings previously reported in the literature have been integrated into a dissociable heuristic framework, which offers a novel representation of subcomponents of the emotion processing system. In considering the development of the subcomponents of emotion processing, evidence indicates that intrinsic arousal systems are operational from birth, systems associated with sensory/spatial skills that are essential in reading emotional expression develop rapidly from birth, and systems utilised in executive system synthesis become increasingly sophisticated with development, stemming across childhood and into adulthood. In conclusion, it is proposed that the heuristic is a useful tool on which assessment measures may be based when considering the primary effects of brain injury in children.