Sufi Allahyar and his work Sebatü’l-Acizin: On Tendencies of Localization in 18. Century Eastern Literary Turkish Sebatü’l-Acizin is a religious and Islamic mystical poem (Mesnevi) of Sufi Allahyar’s. Sebatü’l-Acizin, which is the work of Eastern literary Turkish in XVIII century, is appraised in the post classical period of the Chagatay language. Among the basic principles of the post classical period localization is mentioned. The examples of localization in Sebatü’l Acizin are appraised in this essay. The work differs from the other classical period Chagatay texts with regard to vocabulary, morphology and phonetics. The different sides of this work have been exposed in this essay. The criteria of localization have been tried to determine in Sebatü’l- Acizin. It has been discussed whichever dialects can be connected to these distinctive characteristics in this essay.