Extramedullary plasmacytoma (EMP) is a rare malignancy of the head and neck, accounting for less than 1% of head and neck cancers. EMP of the base of tongue is an even rarer subset of these cases. Still, awareness of its presentation is important in the differential diagnosis of base of tongue masses. We report a case of a 76-year-old male with extramedullary plasmacytoma of the base of tongue. He presented to an outpatient clinic with a small amount of oral bleeding, and flexible nasendoscopy revealed a left base of tongue mass. MRI confirmed a polypoidal lesion arising from the lingual tonsil. A biopsy was taken and histology showed a plasmacytoma. Haematological investigations found no evidence of multiple myeloma, so he was treated with radiation to his base of tongue and neck with complete clinical response on radiological imaging and direct visualisation. There has been no evidence of systemic myeloma or local recurrence in the 27 months since treatment. Base of tongue extramedullary plasmacytoma is a very rare malignancy, but should be considered as a differential diagnosis in cases of a base of tongue mass.