Abstract The aim of the study was to develop a differential diagnostic nutrient medium for the rapid diagnosis of animal dermatophytosis. Abroad, for these purposes, environments such as Dermatophyte Test Medium (DTM) are successfully used, but in Russia such diagnostics has not been developed. As a result of our research, we selected the optimal composition of the nutrient medium, including growth and selective supplements. DTM-Expert, a developed domestic environment for growth, indicator and selective properties, was not inferior to foreign analogues, while it was much cheaper and more ergonomic in use. The widespread introduction of the developed DTM-Expert environment will significantly simplify the diagnosis of dermatophytosis and increase its effectiveness. Also, DTM-Expert can be used to monitor the latent micronization in animals that have no clinical signs of dermatophytosis.