The river takes its source from the central parts of Stara Planina north of Kalofer, it then flows east and makes a sharp turn to the south before Yambol, in which direction it flows until it reaches the Maritsa. The Tundzha's length on Bulgarian territory is 350km. It has about 50 tributaries, the more important of which Mochuritsa, Popovska and Sinapovska.