The Caspian Sea region did not appear as an important hydrocarbon province during the Soviet Union. This is because that Soviet Russia has very rich and exploitable oil and gas reserves in areas outside the Caspian region. The Caspian Sea coastal states as Azerbaijan, Turkmenistan and Kazakhstan, after gained their independence, have prioritized assessing the hydrocarbon reserves of the region in line with their governance policies and have started to include external partners in their exploration and development study. In order to develop the long known hydrocarbon assets of the region, the exploration efforts carried out have enabled the discovery of new fields especially in the Azerbaijan sector of the southern Caspian region. In addition, hydrocarbons discovered in the onshore areas of both Kazakhstan and Turkmenistan have made the southern Caspian region the world’s major hydrocarbon province. The tectonic evolution and petroleum systems of the hydrocarbon-bearing basins called as the North Caspian, Middle Caspian and South Caspian basins in the Caspian Sea region, differ in terms of both essential elements and processes. The most important differences of the South Caspian Basin are rapid deposition of more than twenty-five km thickness sediment fill resulting from an avalanche type sedimentation and the presence of the young Tertiary hydrocarbon source rocks and reservoirs. Therefore, generation-migration, accumulation and trapping processes of the South Caspian Basin petroleum system are still continuing.