Poultry litter mass is formed in large quantities at poultry farms producing poultry meat (1–3 kg of litter mass per 1 kg of produced meat). These wastes represent a threat to the environment because of the presence of pathogenic microflora in them and the greenhouse gas emitted during the storage of these wastes. The procedure of poultry litter mass processing by wet torrefaction in a superheated water vapor environment at a temperature of 150–260 °C is studied. It is shown that after torrefaction at a temperature of 150 °C, the poultry litter mass retains high humidity, i.e., it represents an environment suitable for the re-development of pathogenic microflora. Only after wet torrefaction at a temperature of 260 °C does the humidity of the poultry litter mass decreases to 4%, and the risk of re-infection with pathogenic microflora decreases sharply. The absence of nitrates in the samples after torrefaction at a temperature of 260 °C indicates the termination of the activity of nitrifying bacteria. After torrefaction at a temperature of 260 °C, the poultry litter mass has a pH close to 7. This increases the mobility and availability of microelements for plants. Torrefaction at a temperature of 260 °C increases the content of ash, phosphorus and potassium by 30–40% and nitrogen by 15–20%, which makes the fertilizer more concentrated and optimizes the ratio of nitrogen, phosphorus and potassium. After wet torrefaction, due to the burning of the most easily degradable nitrogen-containing organic compounds and the destruction of some organophosphorus compounds, the mobility of nitrogen decreases, and the mobility of phosphorus increases. As a result of the research, it was found that the treatment of poultry manure by wet torrefaction in an environment of superheated water vapor at a temperature not lower than 260 °C makes it possible to obtain organic fertilizer with the most optimal nutrient content.