A 69-year-old woman, who had been diagnosed as having Sjögren's syndrome at 37 years old and mixed connective tissue disease at 42 years old, was under treatment with oral prednisolone. In 2009, she was diagnosed as having active systemic lupus erythematosus, and started on treatment with tacrolimus at 3 mg/day. In 2010, para-aortic lymphadenopathy and superficial multiple lymphadenopathy were detected. Tacrolimus was discontinued. Axillary lymph node biopsy revealed Epstein-Barr (EB) virus-negative CD5-positive diffuse large B-cell lymphoma (DLBCL). The patient was classified into clinical stage IIIA and as being at high risk according to the international prognostic index. After the discontinuation of tacrolimus, the lymph nodes reduced temporarily in size. In January 2011, the lymphadenopathy increased again, and the patient received a total of 8 courses of therapy with rituximab, pirarubicin, vincristine, cyclophosphamide and prednisolone, followed by intrathecal injection to prevent central nervous system infiltration, which was followed by complete remission. In February 2012, fluorodeoxyglucose positron emission tomography showed relapse in multiple lymph nodes and central nervous system infiltration. The patient was considered to have iatrogenic lymphoproliferative disorder classified as “other iatrogenic immunodeficiency-associated lymphoproliferative disorders” by the WHO, and this is the first reported case of CD5-positive DLBCL and central nervous system infiltration following administration of the drug. The patient was considered to have a poor prognosis as EB virus was negative, discontinuation of tacrolimus was ineffective and there was evidence of central nervous system infiltration. [J Clin Exp Hematopathol 52(3) : 211-218, 2012]