The hallmark of Sweet's syndrome (SS) is the infiltration of mature neutrophils in the upper dermis. We herein report a case of SS with multi-organ involvement. A 32-year-old man presented with fever, anemia and dyspnea. He was given antibiotics, without any improvements. Later, a number of erythematous lesions appeared, accompanied by deteriorating respiratory and cardiovascular functions. A diagnosis of SS was confirmed on a skin biopsy, and the patient was given corticosteroids, the dose of which was reduced after one month. The organ function subsequently deteriorated, and he ultimately died of multi-organ failure. Early recognition of SS with multi-organ involvement is important in patients with SS.