Lymphoma is common in IgG4-related disease, but diffuse large B-cell lymphoma in IgG4-related ophthalmic disease is rare, especially involving the same organ affected by IgG4-related ophthalmic disease. The authors report a 44-year-old man presented with bilateral proptosis for 10 years and rapid loss of vision in the right eye for the last 1 month. The authors performed orbital exenteration for the right eye and resected the tumor in the left eye. Based on the clinicopathologic findings, tumors of the right and left eyes were diagnosed as diffuse large B-cell lymphoma and IgG4-related ophthalmic disease, respectively. This case highlights the risk of malignant transformation of IgG4-related ophthalmic disease.