Phaeohyphomycoses are induced by dematiaceous or darkly pigmented fungi. Alternaria species are the most important causative agents. Factors such as immunosuppression, local wounds or systemic disease are generally present. We report a case of phaeohyphomycosis induced by Alternaria alternata in an immunocompromised patient. The main interest in this case is the rareness of the cutaneous alternariosis and of its clinical aspects and the good response to therapy. Recognition of Alternaria spp. as potential opportunistic pathogens is important for the differential diagnosis of dermatological lesions, such as granulomatous or ulcerative lesions in immunocompromised patients.