Mild traumatic brain injury (mTBI) and sports concussion are a growing public health concern with increasing demands for more rigorous methods to quantify changes in the brain post-injury. Electrophysiology, and in particular Transcranial Magnetic Stimulation (TMS), has been demonstrated to provide prognostic value in a range of neurological conditions; however, no review has quantified the efficacy of TMS in mTBI/concussion. We present a systematic review and critical evaluation of the scientific literature from 1990-2014 that has used TMS to investigate corticomotor excitability responses at short-term (<12 months), medium-term (1-5 years), and long-term (>5 years) post mTBI/concussion. Thirteen studies met the selection criteria, with six studies presenting short-term changes, five studies presenting medium-term changes, and two studies presenting long-term changes. Irrespective of time post concussion, change in intracortical inhibition was the most reported observation. Other findings included increased stimulation threshold, and slowed neurological conduction time. Although currently limited, the data suggests that TMS has prognostic value in detecting neurophysiological changes post mTBI/concussion.