Background: Mild traumatic brain injury (mTBI) is a significant public health concern. Research has shown that mTBI is associated with persistent physical, cognitive, and behavioural symptoms, leading to significant direct and indirect medical costs. Our objective was to determine if age impacts the type and severity of post-mTBI symptoms experienced. Methods: Retrospective analysis of prospectively collected data at a level 1 tertiary care outpatient head injury clinic. Participants (N=167) were patients seen at the clinic following an mTBI. The Rivermead Post-Concussion Symptoms Questionnaire was used to assess symptom severity. Results: In our sample, the mean age was 44±16 years with 51% males. Compared with other age groups, patients >66 years of age were significantly more likely to report an mTBI between 6 AM to 12 PM (69%). Middle-aged patients (36-55 years) were more likely to report higher severity of certain post-mTBI symptoms (headache, nausea and vomiting, irritability, poor concentration, sleep disturbance, blurry vision, light sensitivity, and taking longer to think) compared with patients >66 years of age. Conclusions: In general, middle-aged patients reported higher severity of post-mTBI symptoms compared with the oldest patients. Thus, there was a significant association between age and the severity of specific mTBI symptoms, which highlights the need for targeted management. Additional research is needed to understand the mechanisms that could be contributing to the higher symptom severity experienced by the middle-aged group.