Tibnīn was an important small Crusader fief and a fortified castle. It was vital for the Kingdom of Jerusalem, because it included fertile agricultural lands, was a tax collection centre, and because it controlled the Damascus-to-Tyre commercial route. Additionally, its castle played defensive and offensive role in the north of the Kingdom of Jerusalem and upper Galilee, and its rulers of Tibnīn played a major role in forming the history of the Latin East. When the Crusaders invaded the Levant at the end of the eleventh century, it was given rise to new demographic, cultural, socio-economic, and architectural features. The present Paper aims at removing some of the mystery concerning the fief of Tibnīn and its castle in the Latin East. This paper thus is a study of the demographic structure of Tibnīn and discusses the socio-economic role of Tibnīn in the Latin east. Moreover, the role of Tibnīn in influencing the relations between Muslims and the Crusaders in the Levant and the architecture of the castle of Tibnīn and its importance in the age of the Crusade will be examined.  Citation: Ahmed Mohamed M. Abdelkawy Sheir, “Demographic, Socio-Economic and Architectural Structure of Tibnīn in the Age of the Crusades". - Historical kan Periodical. - Vol. (8) Issue (29); September 2015. Pp. 166 – 177.