During the Qajar dynasty, most Qajar princes ruled one of the regions of Iran. The Nir al-Dowleh family, who were descendants of Parviz Mirza, son of Fath Ali Shah Qajar, were considered the most important ruling family of Nishapur during this period. This research, in the style of historical research, with a descriptive-analytical approach, using sources such as memoirs, newspapers, documents, and oral history and analyzing them, answers the question: What were the reasons for the establishment and continuation of the rule of the Nir al-Dawlah dynasty in Nishapur during the Qajar period, and what were the consequences of this continuation? The research findings indicate that the geographical location and suitable climate of Neyshabur, the numerous properties and high income from these properties, the influence of this family in the court, their relative connection with the Qajar Shah, and the encouragement and willingness of the central government, were influential in the continuation of this family's rule over Neyshabur. Although the rule of the Nir al-Dawlah family over Nishapur was accompanied by the development of the city and the prosperity of agriculture in the land, in some cases it led to the seizure of private and government properties. The injustice and oppression of the rulers of this family, coupled with unusual taxation of the people, placed additional pressure on the people of this region. The separation of the Nishapur government from Khorasan, Independence along with tyranny intensified them. and the Constitutional Revolution also failed to reduce their authoritarian rule.