Abu Sa'id became khan at twelve. The commander Chupan governed in his name, and did it effectively, holding the frontiers and steadying the court. But as the khan grew up the two collided, and with Chupan's removal in 1327 Abu Sa'id finally ruled for himself.
Under him the Ilkhanate signed a peace treaty with its old enemy the Mamluk sultanate of Egypt, ending decades of border war. At home, however, the general families remained powerful, and to the north the Golden Horde was pressing on the Caucasus.
In 1335 he rode north to meet a Golden Horde invasion and died suddenly in camp; the sources split between plague and poison. He left no son, so the direct line from Hülegü ended, and a realm with no agreed way of choosing its next ruler broke into pieces within a year.