The objective of this study was to compare patients with acute-to-subacute mild traumatic brain injury (mTBI) on post-concussion symptom reporting based on whether they retrospectively recalled experiencing pre-injury anxiety or depression. Patients with mTBI ( = 297; 40.4% men; mean = 38.2 years old, standard deviation [SD] = 14.0, range = 17-65), referred from an emergency department in Taipei, Taiwan, were seen in a neurosurgical outpatient clinic on average 7.7 days since injury (SD = 5.7, range = 0 - 21 days), at which time they completed a checklist of post-concussion symptoms. Patients rated their current symptom severity and retrospectively rated their pre-injury symptom severity on 15 physical, cognitive, and emotional symptoms. Patients were grouped based on whether they did or did not have mild or greater pre-injury anxiety or depression based on this scale. Those with pre-injury anxiety or depression had greater pre-injury (all s < 0.001, range: 0.92-2.03) and post-injury (all s < 0.001, range: 0.65-1.00) symptom severity. However, when analyzing perceived change in symptoms (i.e., post-injury ratings minus pre-injury ratings), only perceived change in cognitive symptoms differed across groups ( = 0.018,  = 0.29), which became non-significant after controlling for gender. Greater post-concussion symptom severity in patients with pre-existing mental health problems may be mostly attributable to elevated symptoms before injury. These findings demonstrate the clinical value of retrospective pre-injury symptom assessment in mTBI management. Greater post-concussion symptom severity in patients with pre-injury mental health problems may represent a continuation of greater pre-injury symptom severity rather than a greater increase in symptom severity after mTBI.