It must have been built during the 14th Century for it was in 1370 that the King D.Fernando donated the castle and the town to Gomes Lourenço de Avelar.

Braun & Hogenberg. date c. 1575
COMMENTARY BY BRAUN (on verso): “North of Lisbon lies the town of Cascale, which is particularly suitable as a safe harbour owing to its natural possition with many inlets, since the big ships can find a sheltered anchorage here during rough seas and can wait for a fair wind. […] In a winding bay on the same shoreline lies the small town of Belém with a mighty church that is dedicated to the Blessed Virgin Mary.”

Cascaes
1703 by Germanus Adlerhold

The 1755 earthquake was so vast that reached Cascais and destroyed most of its buidings including the Castle that was never rebuilt.