Dense water formation in the eastern Mediterranean (EMed) is essential in sustaining the Mediterranean overturning circulation. Changes in the sources of dense water in the EMed point to changes in the circulation and water properties of the Mediterranean Sea. Here we examine with a regional climate system model the changes in the dense water formation in the EMed through the 21st century under the RCP8.5 emission scenario. Our results show a shift in the dominant source of Eastern Mediterranean Deep Water (EMDW) from the Adriatic Sea to the Aegean Sea in the first half of the 21st century. The projected dense water formation is reduced by 75% for the Adriatic Sea, 84% for the Aegean Sea, and 83% for the Levantine Sea by the end of the century. The reduction in the intensity of deep water formation is related to hydrographic changes in surface and intermediate water that strengthen the vertical stratification, hampering vertical mixing and thus convection. Those changes have an impact on the water that flows through the Strait of Sicily to the western Mediterranean and therefore on the whole Mediterranean system.