Background: Mild traumatic brain injury (mTBI) is a nationwide problem; yet, no firefighter mTBI data are available. Methods: In this cross-sectional study, we assessed retrospective head injuries using WHO guidelines. We captured mTBI frequency and examined firefighters' symptoms (e.g., using Ohio State University Traumatic Brain Injury Identification method, Brief Traumatic Brain Injury Screen, Warrior Administered Retrospective Causality Assessment Tool). Findings: Of 1,112 firefighters contacted, 60 responses were included. Most participants were White (80%), male (90%), former athletes (75%). 62% met mTBI symptom criteria. 75% reported at least one lifetime head injury. Number of head injuries and depression symptoms were associated (r = .36, p < .05). Conclusion/application to practice: Overall, it appears most firefighters have sustained at least one lifetime mTBI. Those with multiple head injuries may be at increased risk of depression. Occupational health professionals should be aware of firefighters' mTBI risk. Further research is warranted given findings.