Multiple myeloma is a haematologic malignancy characterised by the proliferation of plasma cells and typically presents with lesions in bone, known as plasmacytomas. Through haematogenous spread, extramedullary plasmacytomas can develop in soft tissue in any location of the body. This case report describes a patient with multiple myeloma who presented with an extramedullary plasmacytoma on his maxillary gingiva and provides an updated review on the classification and characterisation of extramedullary plasmacytomas of the oral cavity. A 53-year-old male with a known diagnosis of multiple myeloma was referred to our clinic for evaluation of a gingival nodule, which was tender to palpation and had been present for a month. Clinical examination revealed a 1.5 cm violaceous, red nodule of the maxillary buccal attached gingiva, which did not blanch on palpation. He had a similar 1 cm, smooth, red nodule of his cutaneous skin on his left arm. Radiographic examination was within normal limits without evidence of dental or bony pathology. An incisional biopsy revealed the diagnosis of plasmacytoma, indicating relapse and progression of the patient's multiple myeloma. Multiple myeloma can present in the oral cavity either as intrabony plasmacytomas, paraskeletal plasmacytomas or extramedullary plasmacytomas in the soft tissue. Extramedullary disease representative of haematogenous spread is concerning for high-risk disease with a poor risk prognosis.