The Castle was built in the 14th and 15th centuries on one of many islands of Lake Galvė. The construction of the Castle was started by Grand Duke Kęstutis of Lithuania and finished by his son Vytautas, who died in this castle in 1430. The castle was rebuilt in the 1950s–1960s by Lithuanian initiative, although it had received resistance from Soviet authorities.
Trakai Island Castle was built in several phases. During the first phase, in the second half of the 14th century, the castle was constructed on the largest of three lake islands by the order of Grand Duke Kęstutis. The second phase of construction started and continued until 1409.
The structure of Trakai Island Castle appears to be simple and modestly decorated, thus portraying the consolidation of the 15th century defense ideas. The principal construction material was so-called red Gothic bricks. Stone blocks were used only in the foundations and the upper parts of buildings, towers and walls. The castle was decorated in a variety of ways, including glazed roof tiling, burned bricks, and stained glass windows. Its overall style after the second construction phase could be described as Gothic with some Romanesque features.
It was considered a masterpiece of medieval defensive architecture, and it was the only castle built on water in Eastern Europe.