Magnetic resonance imaging is the imaging method of first choice for evaluating the anatomy and pathology of the brachial plexus. This review discusses the used imaging techniques, the normal anatomy, and a variety of pathologies that can involve the brachial plexus. The pathology includes primary and secondary tumors (the most frequent secondary tumors being superior sulcus tumor and metastatic breast carcinoma), radiation plexopathy, trauma, thoracic outlet syndrome, neuralgic amyotrophy, chronic inflammatory demyelinating polyneuropathy (CIDP), and multifocal motor neuropathy (MMN).