The climatic conditions of Sistan plain and its coexistence paved the way for settlement of human populations, establishment of various residential sites and perhaps more importantly, emergence of civilizations that have given rise to the great cities such as Shahri-Sukhteh and Tang-e Gholaman.Although the accumulation of residential areas in the plain during different times and their proximity to the Hirmand River has attracted archaeologists over the past decades to this culturally rich region but study of hundreds of Islamic sites still remains ambiguous.The present research therefore, studies the distribution and chronology of these sites during Islamic era based on the historical texts, reports of archaeological activities and other related documents and evidence. In particular, it has been attempted to determine the development of Islamic cities in Sistan region and to study their changes during the Islamic era based on the archaeological records. It has also been tried to analyze the functionalities of the major cities of Sistan during the early Islamic period.The results of this research indicate that the capital of Sistan region has moved during Islamic era to be centered in the various cities and the cities such as Zaranj, Shahr-e Sistan, Shahr-e Sistan-e Nou, Jalal-Abaad, Kondark, Sekooheh and Shahr-e Naseri, were in turn appointed as the governmental centres of Sistan during Islamic era in the stated order.