Tinea nigra («black mycosis») is a rare skin mycosis common in endemic areas: Latin America, South Africa, South-East Asia, India, and some other countries. Tinea nigra does not occur in Europe. Anecdotal scientific publications describe rare cases of black mycosis in Spain and the UK. There have been no publications on Tinea nigra in the Russian Federation. We present the first case of Tinea nigra in a 25-year-old man from St. Petersburg. The infection occurred in Sri Lanka due to a minor hand injury. Three dark-colored spots appeared on the palm and fingers of the right hand. Dermatoscopy of the foci showed no evidence of melanocytic mass; no fissures and crest structures were observed. Diffusely scattered brown dots and linear, filamentous structures (spicules) were found on the background of irregular brownish pigmentation. Mycological examination by microscopy with KOH revealed short, curved, often septate, wide, pigmented hyphae and culture growth of Hortaea werneckii. The identification of the pathogen was confirmed by molecular genetic sequencing. The patient was successfully treated with sertaconazole cream. After 4 weeks of therapy, complete mycological and clinical recovery was achieved. Sertaconazole is an imidazole derivative, a broad-spectrum antimycotic with a potent fungicidal effect against most skin mycosis pathogens. Sertaconazole is effective in the therapy of Tinea nigra.