Drug rash with eosinophilia and systemic symptoms (DRESS) syndrome is diagnosed by three criteria including cutaneous drug eruption, hematologic abnormalities, and systemic involvements. The hematologic abnormalities include presence of atypical lymphocytes or eosinophilia. The systemic involvements include lymphadenopathy, hepatitis, interstitial nephritis, interstitial pneumonia, or carditis. We experienced a 41-year-old female patient who presented DRESS syndrome at initial visit, but finally manifested with T-cell lymphoma. The patient complained of erythematous pruritic plaques with itching on her abdomen and thigh. There was no initiating factor and she was diagnosed with urticarial dermatitis. After treatment with antihistamine and systemic steroid, she recovered from skin lesion. However, 1 month later, she came to emergency department with aggravated skin lesion after taking nonsteroidal anti-inflammatory drug for 3 days. On admission, she showed a fever, skin rash, atypical lymphocytes in peripheral blood smear, and hepatitis. She was treated with systemic steroid under the impression of DRESS syndrome. Her symptoms began to improve, however, laboratory parameters were aggravated again. We performed bone-marrow biopsy because of her unusual progress. Finally she diagnosed with peripheral T-cell lymphoma and treated with allo-peripheral blood stem cell transplantation. In conclusion, we report a case of T-cell lymphoma which presented as DRESS syndrome. If patients with DRESS syndrome present lymphadenopathy and atypical lymphocytes, and do not respond to anti-inflammatory treatment, we should consider underlying lymphoproliferative disease.