Previous research suggests that many people who sustain a traumatic brain injury (TBI), even of the mildform, will develop major depression (MD). We previously reported white matter integrity differencesbetween those who did and did not develop MD after mild TBI. In this current paper, we aimed to inves-tigate whether there were also volumetric differences between these groups, as suggested by previousvolumetric studies in mild TBI populations. A sample of TBI-with-MD subjects (N = 14), TBI-without-MDsubjects (N = 12), MD-without-TBI (N = 26) and control subjects (no TBI or MD, N = 23), received structuralMRI brain scans. T1-weighted data were analysed using the Freesurfer software package which producesautomated volumetric results. The findings of this study indicate that (1) TBI patients who develop MDhave reduced volume in temporal, parietal and lingual regions compared to TBI patients who do notdevelop MD, and (2) MD patients with a history of TBI have decreased volume in the temporal regioncompared to those who had MD but without a history of TBI. We also found that more severe MD in thosewith TBI-with-MD significantly correlated with reduced volume in anterior cingulate, temporal lobe andinsula. These findings suggest that volumetric reduction to specific regions, including parietal, temporaland occipital lobes, after a mild TBI may underlie the susceptibility of these patients developing majordepression, in addition to altered white matter integrity.