Sweet's syndrome is extremely rare in relapsing polychondritis. We report a rare case of Sweet's syndrome revealing relapsing polychondritis. A 77-year-old man presented with fever, associated with respiratory symptoms and non pruritic, painful, erythematous, papules and plaques mainly on the arms and legs. Skin biopsy of the arm found a neutrophilic dermal infiltrate consistent with Sweet's syndrome. A month and a half after admission, the patient presented with ear chondritis and dysphonia. Biopsy of the ear cartilage found a significant perichondral inflammatory cells infiltrate. The diagnosis of relapsing polychondritis was established and a steroid treatment was instituted with a complete regression of the cutaneous signs and chondritis.