Background: Outcomes after traumatic brain injury are worsened by secondary insults; modern intensive-care units address such challenges through use of best-practice pathways. Organisation of intensive-care units has an important role in pathway effectiveness. We aimed to assess the effect of a paediatric neurocritical care programme (PNCP) on outcomes for children with severe traumatic brain injury. Methods: We undertook a retrospective cohort study of 123 paediatric patients with severe traumatic brain injury (Glasgow coma scale scores ≤8, without gunshot or abusive head trauma, cardiac arrest, or Glasgow coma scale scores of 3 with fixed and dilated pupils) admitted to the paediatric intensive-care unit of the St Louis Children's Hospital (St Louis, MO, USA) between July 15, 1999, and Jan 15, 2012. The primary outcome was rate of categorised hospital discharge disposition before and after implementation of a PNCP on Sept 17, 2005. We developed an ordered probit statistical model to assess adjusted outcome as a function of initial injury severity. We assessed care-team behaviour by comparing timing of invasive neuromonitoring and scored intensity of therapies targeting intracranial hypertension. Findings: Characteristics of treated patients (aged 3-219 months) were much the same between treatment periods. Before PNCP implementation, 33 (52%) of 63 patients had unfavourable disposition at hospital discharge (death or admission to an inpatient facility) and 30 (48%) had a favourable disposition (home with or without treatment); after PNCP implementation, 20 (33%) of 60 patients had unfavourable disposition and 40 (67%) had favourable disposition (p=0·01). Seven (11%) patients died before PNCP implementation compared with two (3%) deaths after implementation. The probit model indicated that outcome improved across the spectrum of Glasgow coma scale scores after resuscitation (p=0·02); this improvement progressed with increasing injury severity. Kaplan-Meier analysis suggested that neuromonitoring was started earlier and maintained longer after implementation of the PNCP (p=0·03). Therapeutic intensity scores were increased for the first 3 days of treatment after PNCP implementation (p=0·0298 for day 1, p=0·0292 for day 2, and p=0·0471 for day 3). The probit model suggested that increasing age (p=0·03), paediatric risk of mortality III scores (p=0·0003), and injury severity scores (p=0·02) were reliably associated with increased probability of unfavourable outcomes whereas white race (p=0·01), use of intracranial pressure monitoring (p=0·001), and increasing Glasgow coma scale scores after resuscitation (p=0·04) were associated with increased probability of favourable outcomes. Interpretation: Outcomes for children with traumatic brain injury can be improved by altering the care system in a way that stably implements a cooperative programme of accepted best practice. Funding: St Louis Children's Hospital and the Sean Glanvill Foundations.