The aim of this study was to explore the relationship between abnormality on susceptibility-weighted imaging (SWI) and newly-developed depression after mild traumatic brain injury. The study registered 200 patients with closed TBI and normal finding at CT and conventional MRI. All patients underwent MRI including conventional MR sequences and SWI. The number and volume of microbleed lesions were semi-automatically outlined and manually counted. All patients were followed up with the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-IV) within 1 year after TBI. The difference in microbleed lesions on SWI was compared between the depressive and non-depressive groups. The depressive group had a higher rate of abnormality on SWI than did the non-depressive group (p < 0.001). Among patients that had exhibited microbleed lesions, the number and volume of lesions were greater in the depressive group than the non-depressive group (both p < 0.001). These differences in numbers and volume of lesions were found only at the frontal, parietal and temporal lobes (all p < 0.001). Among patients that had exhibited microbleed lesions, the number and volume of lesions in other areas were not significantly different between the depressive and non-depressive groups (all p > 0.05). In conclusion, SWI was useful to identify the microbleed lesions after mild TBI. The distribution range and location of microbleed lesions were correlated with depression after TBI.