Objective: Age is assumed to be a negative prognostic factor in recovery from moderate-to-severe traumatic brain injury (TBI). Little is known on cognitive performance after mild TBI in relation to age in the sub-acute stage after injury. Method: Ninety-nine mild TBI subjects (age 15-75) were compared with 91 healthy control subjects (age 14-74) in a case-control design. Patients were matched on age, sex and level of education, with control subjects. Mean interval between injury and cognitive assessment was 13 days. Neurocognitive test battery contained tests of verbal memory, selective attention, general speed of information processing and verbal fluency. Results: An overall effect was found of a single mild TBI on neurocognitive performance in the sub-acute stage after injury. Age did not add significantly to the effect of mild TBI on cognitive functioning. Conclusion: Patients suffering from mild TBI are characterized by subtle neurocognitive deficits in the weeks directly following the trauma. The notion that elderly subjects have a worse outcome in the sub-acute period after mild TBI is at least not in line with the results of this study.