The resort was established under the Health Commissariat of the Azerbaijani SSR in 1925, after the Red Army invasion of Azerbaijan and the subsequent Sovietization of the country. It began to operate in 1927. In 1951, baths and a resort hospital and a hotel were built in Upper Istisu. In 1970, the Soviet government included the Istisu resort in the list of resorts that had all-union importance. During the Soviet period, 50 thousand people were treated here every year. In the 1980s, a water filling plant was built as part of the sanatorium. More than 800 thousand litres of mineral water were produced daily from the mineral water fields located here.