Previous investigations of long-term outcome following traumatic brain injury (TBI) have yielded mixed results regarding the predictive power of injury severity and demographic factors. Furthermore, there has been limited investigation of the association between long-term outcome and current cognitive functioning and psychiatric state. The aim of this study was to investigate the association of injury severity, demographic factors, and concurrent cognitive and psychiatric functioning with functional outcome 10 years following mild to severe TBI. Outcome was rated using the Extended Glasgow Outcome Scale (GOSE) for 60 participants, who also completed neuropsychological measures of attention, speed of processing, memory and executive function and the Hospital Anxiety and Depression Scale (HADS). Outcome on the GOSE ranged from upper good recovery (32%) to lower severe disability (2%). Participants showing poorer outcome on the GOSE had significantly longer posttraumatic amnesia duration; less education; performed more poorly on cognitive measures of information processing speed, attention, memory, and executive function; and showed higher levels of anxiety on the HADS.