The subject of this study focuses on the internal and external developments that took place in the Khorasan region and the eastern regions of the Great Seljuk State after Sultan Sencer ascended to the throne in 1118. In the study, in addition to the internal conflicts and throne fights in the Seljuk State, the struggles and activities of Sultan Sanjar, especially regarding the Abbasid Caliphate, Ghaznavids, Kara-Khitays and other foreign issues, until he was captured by the Oghuzs, were discussed. The fact that Sultan Sencer had an important place in Turkish history as the last ruler of the Seljuk State and played a fateful role for the Seljuk State increases the importance of the period covered.