Geothermal energy originates from the depths of the Earth, where heat accumulates from various sources, such as the decay of radioactive elements. This heat is transferred to the Earth's surface via geothermal waters through complex thermal processes of convection and conduction. Geothermal waters are natural waters that come from hot springs, usually from geothermal areas. These are waters that throughout the year have a temperature higher than the average annual air temperature in the area of their source. Geothermal water sources differ primarily in terms of water temperature, aquifer and method of use. Considering the temperature of geothermal waters, there is a division into 4 categories: subthermal, hypothermal, homeothermal and hyperthermal waters. The aim of this work was to determine the quality of the thermal waters of Krapinske Toplice. Sampling was carried out at 4 locations: Jakobova kupelj, Pu ka kupelj, Topli ina stream and the pump at Pu ka kupelj. Temperature, pH value, concentration of total dissolved substances and electrical conductivity were measured at the sampling sites. The thermal water samples were then transported to the laboratory, where the determination of the concentration of the main cations and anions, the concentration of trace elements, and COD and BOD5 was carried out. The analysis of thermal water samples found that the values of the tested parameters are within the maximum allowed concentrations in accordance with the Ordinance on compliance parameters for water intended for human consumption.