The brick ornamentation in Islamic architecture represents the unique skill of the architectural artists and we have seen the perfection of this kind of art during the Seljuk period. There is little information about the process of developing brick art in the architecture of Islamic mosque in Iran, and it has not yet been dealt with as it is worthy of this precious art. Therefore, it is necessary to carry out further research in this regard due to its importance in Iranian architecture. In this research, through library studies and with a descriptive-analytical approach, the trend of development of bricks ornament in the architecture of the Islamic mosques of Iran from the beginning to the end of the Ilkhan era, as well as the causes of importance and development to the bricks of the Seljuk period were studied. The brickwork decoration in the Islamic architecture of Iran gradually begins from the third century A.H. Generally speaking, the early Islamic centuries can be considered as the formation and development of brickwork ornamentation, which reaches its peak in the Seljuk era, thus the richest brick-making projects develops in this era, because during this period, artists managed to create numerous works and structures with the element due to the calm and stability of the Seljuk territory. After this period, bricklaying works continued during the Kharazmshahi era in the Khorasan area, and in the course of the Ilkhani period, its development was reduced and other techniques such as acrography and tiling were popularized.
