Hanafī jurist and Ash'arī theologian Abū Djafar al-Simnānī (d. 444/1052) played an important role in the period in which he lived. The aim of this article is to determine Simnānī's place in Islamic thought and in particular in Ash'arism. The author's ideas and world of thought are determined by the method of focusing on the person. In addition, this article, sheds further light on some opinions about the author based on his only surviving work thanks to cross-readings made from different sources. Simnānī, who lived right after the establishment of Ash'arism, followed Bāqıllānī's system and was instrumental in transferring his thoughts to the West and especially to Andalusia. In this study, determinations are made about the status of the “Bāqıllānī tradition” followed by Simnānī and the development of this tradition. In addition, the details of the views attributed to Simnânî on issues such as the attributes of Allah, the institution of prophethood and the virtue of Muhammad and his ideas on these issues are examined. This article seeks to demonstrate that Simnānī is an important link in the chain of the historical development of eleventh century Ash'arī thought. Our study shows that his work al-Bayān an usūl al-īmān is a valuable work that reflects the characteristics of “classical and theological Ash'arism”.