Exploration of the injured brachial plexus is very hard due to the close approximation with other vital structures and the anatomic complexity. It is essential to identify the exact level and type of traumatic brachial plexus injury (BPI) to decide the appropriate surgical approach for the injury and to infer the postoperative prognosis. However, it can be difficult to image the brachial plexus because of the anatomic properties. The purpose of this study is to analyze the diagnostic value of MRI according to various planes of the level and the type of the traumatic BPI. In sixty patients with traumatic BPI, whose diagnosis was confirmed by clinicopathological and surgical findings, the preoperative MRI films were reread retrospectively. Brachial plexus injuries were divided into two groups of preganglionic BPI and postganglionic BPI, and then postganglionic BPI was divided into 3 subgroups of Zone I, Zone II and Zone III by major adjacent structures such as scalenus anterior muscle and pectoralis minor muscle. The accuracy of MRI was investigated with the confirmed diagnosis on axial, sagittal and coronal planes. In preganglionic BPI, the accuracy of MRI was 96% on axial plane and it was statistically significant compared to sagittal and coronal planes. In postganglionic BPI, the accuracy of MRI was 100% on sagittal plane and 86% on coronal plane in Zone I, but it was not significant statistically. In Zone II and III the accuracy of MRI were 89% and 80% on sagittal plane, and 61% and 60% on coronal plane, but it was not significant statistically. In conclusion, the MRI can provide useful guidance to diagnose preganglionic and postganglionic BPI. Axial imaging is considered better for preganglionic lesion and sagittal imaging for postganglionic BPI, but it demands further study on larger number of subjects with traumatic RPI.