Magnetic resonance (MR) imaging has become the method of choice for evaluating patients with brachial plexopathy. The multiplanar capability of MR imaging and its superior ability to differentiate nerves from vessels and surrounding soft tissues contribute to its success. The article describes the MR anatomy of the brachial plexus in the axial, coronal, and sagittal planes and reviews the MR characteristics of traumatic and nontraumatic etiologies of brachial plexopathy.