One of the breaking points in Turkish and Islamic history is the Battle of Dandanakan, which took place between the Seljuks and the Ghaznavids in 1040. After the war, the Seljuks became an effective and decisive power, especially in the Sunni Islamic geography with a rapid rise. The Great Seljuk Empire, which came from a nomadic culture and irrepressibly expanded its domination from Turkistan to Anatolian territory in a very short time while it was in the nature of a nomad group, started to mature institutionally as well. At this point, the Persian origin statesmen, many of whom previously served in the state organization of Ghaznavid, met the need for trained personnel that emerged both in the central government and in the provinces. One of these names is Hasan b. Ali b. Isḥāq al- Ṭūsī, who will become famous with the name of Niẓām al-Mulk and will get ahead of his original name. Niẓām al-Mulk has been an extremely effective name in the institutionalization of the Great Seljuk State with the steps and actions which he tookin the military, administrative, scientific, and economic fields at a time when the state power was depended on victories in the military field. As a result of that event, he gained a respectable place among both public and statesmen. Within the scope of this study, the position of Niẓām al-Mulk in the state bureaucracy, his relations with the rulers and dynasty members, and the reflections of the actions taken by him from his period of vizier to the Seljuk history will be discussed.