Onychomicosis, one of the most common dermatological diseases, is a serious sociomedical problem. According to modern epidemiological data, more than half of all pathologies of the nail apparatus are caused by fungal infection. Treatment of onychomycosis presents significant difficulties despite the wide range of available therapeutic agents. Topical antimycotic drugs demonstrate limited efficacy, while systemic therapy is associated with potential adverse events and drug interactions. Photodynamic therapy (PDT) is of particular interest in the context of search for innovative and safe treatment methods for onychomycosis. The method is based on the combined application of photosensitizing agents followed by exposure to visible light, which induces photochemical reactions leading to the death of pathogenic microorganisms. We present the clinical observation of a patient (69 years old) with common onychomycosis caused by yeast and mold fungi. According to the anamnestic data, the use of systemic antimycotics was not effective enough. Taking this into account, it was decided to perform a course of PDT procedures for the patient using a gel containing chlorin e6 derivative as a photosensitizing agent. The obtained results show the high efficacy of PDT. The clinical and mycological remission achieved in the patient allows us to consider this medical technology as a promising method of onychomycosis treatment, especially in cases of resistance to standard therapeutic agents. Further research in this area is highly relevant. The improvement of PDT schemes will allow to develop optimal treatment protocols and improve the quality of life of patients with onychomycosis.