A 34-year-old Thai man presented with a two years history of progressively enlarged lepromatous leprosy like nodules and plaques on his back, chest, and scalp. Skin biopsy showed diffuse nonnecrotizing granulomatous inflammation with numerous multinucleated giant cells, lymphocytes, and plasma cells infiltration. The missed diagnosis of leprosy was made and was treated with antilepromatous drugs for one year. After repeated skin biopsy, the diagnosis was compatible with sarcoidosis. He was treated with prednisolone 40 mg per day for two weeks. The lesions gradually decreased in size and were controlled with prednisolone 10 mg per day.