The Friday mosque of Faryūmad is located in eastern Iran (the Khurasan region). Ilkhanid written sources, such as Nuzhat al-Qulūb by Ḥamdullāh Mustaufī (1281–1344), recount that Faryūmad was known as the centre of Juvayn. Earlier Saljuq sources (e.g. Tārīkh-i Bayhaq) note that Faryūmad was a large district and had its own governor in the period prior to reaching its significance in the Ilkhanid period. Despite the monument’s significance for the understanding of the evolution of construction technology from the Saljuq to the Ilkhanid period, it lacks consistent research. This paper proposes the first systematic analysis of the monument’s epigraphic corpus and includes its full documentation. It suggests new information regarding the history and patronage of the Faryūmad Friday mosque. The examination of historic inscriptions of the monument also provides new information regarding the identity of the patron of the mosque. Furthermore, examination of inscriptions and stucco revetments allows for a revised chronology of the construction and decorative phases of the monument.