The monastery was built to thank the Virgin Mary for the Portuguese victory over the Castilians in the Battle of Aljubarrota in 1385, fulfilling a promise of King John I of Portugal.

Work on the convent continued into the reign of John III of Portugal with the addition of the fine Renaissance tribune (1532) by João de Castilho.

In 1840, king Ferdinand II of Portugal started a restoration program of the abandoned and ruined convent, saving this jewel of Gothic architecture.

The western façade, facing the large square with its equestrian statue of general Nuno Álvares Pereira, is divided in three by buttresses and huge pilasters: the Founder's Chapel (Capelo do Fundador), the side wall of an aisle and the projecting portal.

The portal shows in the archivolt a profusion of 78 statues, divided over six rows, of Old Testament kings, angels, prophets and saints, each under a baldachin.

But the Manueline, ogival stained-glass windows in the choir date from the 1520s and 1530s and were produced by Portuguese masters, among them Francisco Henriques.

They represent scenes from the lives of Jesus and Mary: the Visitation, the Epiphany, the Flight into Egypt and the Resurrection of Christ.

The tomb of the knight Martim Gonçalves de Maçada, who saved the king's life during the battle at Aljubarrota, can be found close to the Capela do Fundador.

The square Founder's Chapel (Portuguese: Capela do Fundador) was built between 1426 and 1434 by the architect Huguet on orders of King John I to become the first royal pantheon in Portugal.

The chapel consists of three notional bays and a central octagon buttressed by eight piers, adorned with crockets, supporting deeply stilted arches.

The joint tomb of King John I of Portugal (d. 1433) and his wife Philippa of Lancaster (d. 1415) stands under the star vault of the octagon.

Their statues lie in full regalia, with clasped hands (expressing the good relations between Portugal and England) and heads resting on a pillow, under elaborately ornamented baldachins.

On the cover plate of the tomb are inscribed in repetition the mottos of the king Por bem ("for the better") and of the queen Yl me plet ("I am pleased").

At the south wall stand a row of recessed arches with the tombs of the four younger sons of John I, together with their spouses.

From left to right: Ferdinand the Holy Prince (a bachelor, he died a prisoner in Fez in 1443; his bodily remains were later recovered and moved here in 1473); John of Reguengos, the Constable of Portugal (d. 1442), with his wife Isabella of Barcelos (d. 1466); Henry the Navigator (under a baldachin, d. 1460, a bachelor); and Peter of Coimbra (regent for Afonso V, 1438–1448, who was killed at the Battle of Alfarrobeira in 1449; his remains were moved here in 1456) with his wife Isabella of Urgell (d. 1459).

The original design, begun by Huguet, was altered by successive architects, especially Mateus Fernandes (who is buried inside the church).

It is completely decorated into a lacework of sumptuous and stylized Manueline motives: armillary spheres, winged angels, ropes, circles, tree stumps, clover-shaped arches and florid projections.

The colonettes, supporting these intricate arcade screens, are decorated with spiral motives, armillaries, lotus blossoms, briar branches, pearls and shells and exotic vegetation.

Situated in the northwestern corner of the Claustro Real, this work of Mateus Fernandes consists of a fountain and two smaller basins above, illuminated by light seeping through the intricate tracery of the arches around it.

This sober cloister next to the Claustro Real was built in conventional Gothic style with double pointed arches.