At the beginning of the eighth century, occupied by the Muslims, who called as "Chantirein" or "Chantarim" kept its urban structure and strengthened its agricultural, commercial and administrative vocation.

The town and its castle were in the path of the Almohad caliph Abu Ya'qub Yusuf I, who attacked the village in 1171 in hopes of expanding.

Under the reign of Ferdinand (1367-1383), the sovereign commissioned the strengthening and expansion of the defenses, such as the reform of the port of Santiago in pointed arch in 1382.

John I of Castile put on the walls of Santarém a Castilian garrison, and the region only returned to Portuguese hands immediately after the battle of Aljubarrota (1385).

One last Infante D. Afonso, Prince of Portugal would mark the history of the town and its castle: some scholars point out the death of the son of John II (1481-1495), in a tragic riding accident in Mouchão of Alfange on the banks of the Tagus River ( 1491), as one of the reasons for the departure from the Court of Santarém village and its consequent decline of administrative importance in the kingdom.