Archaeological evidence places human settlement in the Braganca region as far back as the Paleolithic. During the Neolithic, communities grew around agriculture and animal domestication, leaving behind ceramics, arrowheads, and modest jewelry forged from stone. Megalithic constructions dot the surrounding landscape. The Romans upgraded an existing fort during their time in Iberia, but the fortification fell to ruin when Muslim forces arrived and rebuilt it entirely. The earliest written reference to a settlement resembling the name Braganca appears in the acts of the Council of Lugo in 569 AD, where it was called Vergancia. A later Visigothic reference from King Wamba called it Bregancia, a place that supposedly gave birth to two Christian martyrs named John and Paul.

The castle's medieval history reads like a ledger of Portuguese power struggles. Under King Denis in 1293, the village erected a walled perimeter, signaling prosperity. His successor Afonso IV seized the assets of his illegitimate brother, provoking a rebellion in which Afonso Sanches invaded Braganca and left enormous damage. During the 1383-1385 succession crisis, the town's mayor refused to take sides. Castile seized the territory, but King John I recovered it through the Treaty of Segovia in 1400 and massively reinforced the defenses. The marriage of Afonso, the 1st Duke of Braganza, to Beatriz, daughter of the national hero Nuno Alvares Pereira, established the House of Braganza here, a dynasty that would eventually rule Portugal and Brazil. Under Afonso V, the settlement was elevated to city status.

The castle endured more than political intrigue. During the Portuguese succession crisis of 1580, Braganca backed the losing side. The War of Restoration and the Seven Years' War both brought damage. Yet the eastern section, rebuilt before the Peninsular War, successfully repulsed Napoleonic troops. The physical structure tells its own story: an ovoid plan with walls two meters thick enclosing three hectares, reinforced by fifteen turrets, with a perimeter of 660 meters. The keep houses the Church of Santa Maria and a medieval pillory. From the battlements, the mountains of Montesinho rise to the north, Sanabria to the west, and the Castle of Rebordoes is visible to the east. Beyond the legends of the princess tower, darker history clings to these walls. Sancha, sister of Portugal's first king Afonso Henriques, reportedly took refuge here from her unfaithful husband. Centuries later, D. Leonor, wife of the fourth Duke of Braganca, was accused of adultery by her husband. He murdered her at the Ducal Palace in Vila Viçosa on November 2, 1512.

The castle was classified as a National Monument in 1910. Extensive restoration of the walls followed under the General Directorate of National Buildings and Monuments, and since 1936 a military museum has occupied the keep. The construction itself speaks of the region: walls of masonry shale rock, abundant in the hills of Tras-os-Montes, mark every corner and opening. The original drawbridge has long since decayed, replaced by a heavy wooden door. On the southern side, a gun stone bears the coat of arms of the House of Avis. The battlements are crowned with cruzetadas, and cylindrical watchtowers at the four corners still command views across the valley. Braganca remains one of Portugal's most remote cities, and the castle stands above it as it always has, a fortress shaped by every hand that tried to take it.