Alitretinoin is an endogenous panagonist known to bind all recognized retinoid receptors (RAR/RXR) mediating antiproliferative along with immune-modulating proaptotic effects. Recently, a number of cases have been reported indicating the efficacy of alitretinoin in treating mycosis fungoides. A 47-year-old man presented with a history of intractable pigmented and brownish patches and plaques on whole body for 4 years. The patient had undergone gastrectomy in 2011 due to pervious gastric cancer and has not recurred since the surgery. The histopathology revealed epidermotropism with Pautrier``s microabscess and large cell transformation was observed with CD30 (+) on immunohistochemical analysis. Based on these clinical and histopathological results, the patient was diagnosed with large cell transformed mycosis fungoides. The skin lesion was intractable and had aggravated to an ulcerative form despite treatment such as topical steroids, UBV phototherapy and Methotrexate. Alitretinoin was then administered in combination with UBV phototherapy and topical steroid. After two months, the patient showed significant improvement on the skin lesion with only few brownish hyperpigmented patches left. Herein, we report a rare case of large cell transformed mycosis fungoides successfully treated with alitretinoin.