Phaeohyphomycoses are a heterogeneous group of rare mycotic infections caused by dematiaceous fungi. They are classified into four forms: superficial, cutaneous and corneal, subcutaneous, systemic. Alternaria species are ubiquitous fungi that are occasionally aetiological agents of pheohyphomycosis. A case of onychomycosis caused by Alternaria alternata treated with itraconazole is reported.