We report a patient with sarcoidosis who developed diffuse large B-cell lymphoma. A 71-year-old woman with persistent cough was diagnosed pathologically with sarcoidosis by resection of the right upper lung lobe with a nodule after an unsuccessful attempt of transbronchial needle aspiration for mediastinal lymphadenopathy. She was referred for an eye examination and found to have spotty retinal degeneration on the lower fundi of both eyes, together with residual macular edema and vitreous opacity in the left eye. At 76 years, she underwent cataract surgery and vitrectomy to gain a visual acuity of 0.6 in the left eye. At 77 years, she developed a cough and fever, and showed leukopenia and thrombocytopenia. Computed tomography showed multiple small nodular lesions in both lungs, and bilateral hilar, mediastinal, and hepatic lymphadenopathy. Fluorodeoxyglucose positron emission tomography demonstrated high uptake in the liver, spleen, pancreatic head, and lymph nodes. Bone marrow biopsy was intact, but liver biopsy revealed anomalous large lymphoid cells in the sinusoids which were positive for CD20 and showed a high Ki-67 index, leading to the diagnosis of diffuse large B-cell lymphoma. Chemotherapy with 8 courses of THP-COP (cyclophosphamide, pirarubicin, vincristine, and prednisolone) with rituximab, followed by intrathecal injection of methotrexate, cytarabine, and dexamethasone, resulted in complete remission. She maintained complete remission for 10 years until 88 years old at present. The literature review found 30 patients, including this case, who developed lymphoma in the course of sarcoidosis. A novel pathological diagnosis is required in the setting of acute symptomatic changes and novel lesions on imaging in patients with sarcoidosis.