Diffusion Kurtosis Imaging (DKI) allows for studying microscopic changes in human brain tissue. In traumatic brain injury (TBI), this may include axonal stretching, shearing, or swelling. Particularly in mild TBI cases, effects can be subtle and standard imaging modalities fail. We study DKI in 68 mild TBI patients with normal structural imaging in a series of four exams over a 90-day period. Using tract-based spatial statistics (TBSS) we observed increased kurtosis five to ten days post-injury followed by decreased kurtosis three months later. Diffusion tensor metrics such as fractional anisotropy in this study lack the sensitivity to track microstructural changes.