We report the case of a primary nasopharyngeal interdigitating dendritic cell tumor (IDDCT). A 25-year old male presented with bilateral decreased hearing, double vision, and ataxia. Flexible nasopharyngoscopy reviewed a large mass obstructing and filling the entire nasopharynx. MRI and PET-CT confirmed the presence of the primary tumor and demonstrated bilateral cervical lymphadenopathy. Biopsy of the nasopharynx revealed a hematolymphoid neoplasm with dendritic cell differentiation, most consistent with an IDDCT. The lesion was unresectable. The patient was treated with definitive radiotherapy to 66 Gy to the primary tumor and 50 Gy to the bilateral cervical lymphatics using an IMRT technique. A complete response was achieved and the patient remains disease free at the primary site 23 months after completion of radiotherapy.