The authors describe a case of onychomycosis by Paecilomyces lilacinus in an 81-year-old Caucasian woman. The infection was characterized clinically by yellow-brown discoloration of the nail plate, distal-lateral onycholysis and subungual hyperkeratosis of the first left toenail. Microscopic examination showed irregular hyphae. Four cultures showed the development of lilac and powdery colonies. Conidiophores with divergent long narrow terminal phialides were observed at microscopic examination of culture samples. Therapy with amorolofine nail laquer, itraconazole and terbinafine was uneffective. This is the sixth case published in the literature of Paecilomyces lilacinus onychomycosis, and the second Italian case of Paecilomyces lilacinus infection.