MRI has been used increasingly in the evaluation of nasopharyngeal carcinoma (NPC) because of its good tissue contrast and multiplanar capacity. Although there are some controversies in assessing skull base invasion and cervical metastatic adenopathy, recent reports demonstrate that MRI is currently better than or as good as CT in defining the extent of NPC. During follow-up of patients with NPC after radiotherapy, MRI is also more effective than CT in demonstrating tumor recurrence and in detecting postradiation complications. However, the difficulty of using MRI to detect early mucosal recurrence and to differentiate postradiation tissue changes from local tumor recurrence should be recognized. This paper reviews the literature regarding MRI of NPC related to radiotherapy, with special emphasis on treatment planning, recurrence assessment, and complication detection.