Mild traumatic brain injury (MTBI), or concussion, is one of the least understood injuries facing the neuroscience and sports medicine community today. The notion of transient dysfunction and rapid symptom resolution is misleading since symptom resolution is not indicative of injury resolution. Our working hypothesis is that there are residual postural and EEG abnormalities in concussed individuals that could be reliably assessed using appropriate research methodology. This paper presents combined postural and electroencephalographic (EEG) findings suggesting the persistent functional deficits in athletes suffering from MTBI. Twelve concussed athletes and twelve normal controls participated in the study. There was a decrease in EEG power in all bandwidths studied in concussed subjects, especially in standing postures. This was accompanied by sustained postural instability especially under the no vision testing condition. Overall, this study demonstrated the presence of long-term functional abnormalities in individuals suffering from mild traumatic brain injury.