A frequent consequence of traumatic brain injury (TBI) is cognitive impairment, which results in significant disruption of an individual's everyday living. To date, most clinical rehabilitation interventions still rely on behavioral observation, with little or no quantitative information about physiological changes produced at the brain level. Functional brain imaging has been extensively used in the study of cognitive impairments following TBI. However, its applications to rehabilitation have been limited. This is due in part to the expensive or invasive nature of these modalities. The objective of this study is to apply functional near-infrared spectroscopy (fNIR) to the assessment of attention impairments following TBI. fNIR provides a localized measure of prefrontal hemodynamic activation, which is susceptible to TBI, and it does so in a noninvasive, affordable and wearable way, thus partially overcoming the limitations of other modalities. Participants included 5 TBI subjects and 11 healthy controls. Brain activation measurements were collected during a target categorization task. Significant differences were found in the hemodynamic response between healthy and TBI subjects. In particular, the elicited responses exhibited reduced amplitude in the TBI group. Overall, the results provide first evidence of the ability of fNIR to reveal differences between TBI and healthy subjects in an attention task. fNIR is therefore a promising neuroimaging technique in the field of neurorehabilitation. The use of fNIR in neurorehabilitation applications would benefit from its noninvasiveness and cost-effectiveness and the neurophysiological information obtained through the evaluation of the hemodynamic activation could provide invaluable information to guide the choice of intervention.