In response to the need to better define the natural history of emerging consciousness after traumatic brain injury (TBI) and to better describe the characteristics of the condition commonly labeled Post-traumatic Amnesia, a case definition and diagnostic criteria for the Post- traumatic Confusional State (PTCS) were developed. This project was completed by the Confusion Workgroup of the American Congress of Rehabilitation Medicine Brain Injury Interdisciplinary Special Interest group. The case definition was informed by an exhaustive literature review and expert opinion of workgroup members from multiple disciplines. The workgroup reviewed 2,466 abstracts and extracted evidence from 44 articles. Consensus was reached through teleconferences, face-to-face meetings, and three rounds of modified Delphi voting. The case definition provides detailed description of PTCS (1) core neurobehavioral features, (2) associated neurobehavioral features, (3) functional implications, (4) exclusion criteria, (5) lower boundary, and (6) criteria for emergence. Core neurobehavioral features include disturbances of attention, orientation, and memory as well as excessive fluctuation. Associated neurobehavioral features include emotional and behavioral disturbances, sleep-wake cycle disturbance, delusions, perceptual disturbances and confabulation. The lower boundary distinguishes PTCS from the minimally conscious state while upper boundary is marked by significant improvement in the four core and five associated features. Key research goals are establishment of cut-offs on assessment instruments and determination of levels of behavioral function that distinguish persons in PTCS from those who have emerged to the period of continued recovery.Copyright © 2020. Published by Elsevier Inc.