Extramedullary plasmacytoma of the larynx is rare, especially when coexisted with squamous cell carcinoma in situ. We report a 56-year-old woman with hoarseness for 6 months and dysphonia for a week. Fiberoptic laryngoscopic examination showed a red, smooth-surface swelling in the submucous region of the left ventricle and ventricular band of the larynx. The patient underwent vertical laryngectomy and modified left neck dissection. Postoperative pathologic examination revealed coexisting plasmacytoma and carcinoma in situ. Bone marrow biopsy and systemic radiogram showed no positive findings. The hepatic and renal functions were normal. Monoclonal immunoglobulin light chain of type kappa was detected in urine. Hence, a laryngeal extramedullary plasmacytoma with carcinoma in situ was diagnosed. No recurrence or progression was observed during a 2-year follow-up. Here, we discussed the risk factors, diagnosis, and therapy for this rare disease. Extramedullary plasmacytoma of the larynx is rare, especially when coexisted with squamous cell carcinoma in situ. We report a 56-year-old woman with hoarseness for 6 months and dysphonia for a week. Fiberoptic laryngoscopic examination showed a red, smooth-surface swelling in The submucous region of the left ventricle and ventricular band of the larynx. The patient underwent vertical laryngectomy and modified left neck dissection. Postoperative pathologic examination revealed coexisting plasmacytoma and carcinoma in situ. Bone marrow biopsy and systemic radiogram showed no positive findings. The hepatic and renal functions were normal. Monoclonal immunoglobulin light chain of type kappa was detected in urine. Therefore, a laryngeal extramedullary plasmacytoma with carcinoma in situ was diagnosed. No recurrence or progression was observed during a 2-year follow-up. Here, we discussed the risk factors, diagnosis, and therapy for this rare disease.