Scant research has examined the relationship between posttraumatic confusion (PTC) and cooperation during rehabilitation from moderate to severe traumatic brain injury. In this study, PTC and cooperation were examined in a prospective cohort of 74 inpatients with traumatic Brain Injury. Confusion was measured using the Confusion Assessment Protocol. Cooperation was rated on a 0-100 scale by rehabilitation therapists. Using multiple regression analysis, PTC significantly predicted cooperation (R(2) = 0.33, P < 0.001). Age at injury, education, days since injury, and Glasgow Come Scale scores were not significant predictors. Bivariate analyses indicated that four PTC symptoms significantly predicted poorer cooperation: daytime hypersomnolence (ρ = -0.42, P < 0.001), agitation (ρ = -0.39, P = 0.001), psychosis (ρ = -0.39, P = 0.001), and cognitive impairment (ρ = -0.24, P = 0.04). Results provide empirical support that PTC is associated with poorer cooperation and empirical justification for interventions to manage confusion during early recovery from traumatic brain injury.