Abstract <p>This paper presents a brief overview of the current understanding of the main causes of Caspian Sea level (CSL) changes that occur as a result of disruption of the sea’s water balance. The main reason for changes in the water balance is regional climate change in the Caspian Sea region and in its vast catchment area. It includes changes in precipitation, evaporation, river runoff, and runoff into the Kara–Bogaz–Gol Bay. Other causes discussed in the literature are also considered: cosmogeophysical, geological–geodynamic, and anthropogenic. The chronology of CSL changes shows that its level is difficult to predict for the long term, despite its fairly simple water balance. Due to the enormous ecological and economic significance of long–term changes in the CSL, its forecast for the coming decades remains a strategic task in the context of the ongoing sea level decline that began in 1995–1996. The drop in the sea level by about 2.7 m has already led to tangible environmental and socioeconomic consequences for all Caspian countries.</p>