Research pertaining to the occurrence of depression and/or depression symptomatology after a Mild Traumatic Brain Injury (MTBI) was reviewed. We found that methodological differences such as the criteria used to assess MTBI and depression, time that elapsed since brain injury, and control group variations confounded comparisons across studies. Nevertheless, the studies are consistent with at least a 35% prevalence of, and left frontal damage with depression after MTBI, an overlap of symptoms of depression and Postconcussion Syndrome (PCS), and indicate that depression can continue for many years following the injury. Our conclusion is that MTBI is the triggering event for a set of pathophysiological changes and a concomitant depressive episode in a vulnerable subset of the population. Due to a paucity of research, it cannot be definitively concluded that the underlying substrates of depression seen after MTBI and clinical depression are the same. Implications for future investigations are discussed.