Gynecomastia (GM) is a benign condition characterized by enlargement of the male breast, which is attributed to proliferation of the glandular tissue and local fat deposition. We present here a case with unilateral GM that gradually developed after cadaveric renal transplantation. A 37-year-old man who underwent renal transplantation in 2010 was admitted to our center with complaints of unilateral right-sided GM. There was no nipple discharge, pain or redness in the affected breast. His graft was functioning well. His medications consisted of Cyclosporine (CsA) at a dose of 200 mg/d, mycophenolic acid at a dose of 2000 mg/d, prednisolone at a dose of 5 mg/d, doxazosin 8 mg/d, and metoprolol 50 mg/d. CsA-induced GM was considered, and CsA was switched to sirolimus. After two months, GM regression was not observed. Fine needle aspiration of a right breast mass revealed a benign condition. Estrogen and progesterone receptor was strongly positive on microscopic examination of the tissue. GM is a rare condition that is generally caused by CsA treatment. However, GM may persist after the discontinuation of CsA.