The first known residence of the Károlyi family in Carei dates back to the end of the 15th century. It must have been a solid building, with elements of fortification, given the fact that the nobility of the county considered it to be a threat and asked the king to demolish it.
Owing to its strategic position and consolidated forms, in the 17th century, the citadel from Carei was part of the defense fortification system against the Turks. In order to successfully face a potential attack, between 1661 and 1666 the walls of the fortress were extended, and after the restoration, a German garrison was detached having its own artillery.
After Sándor Károlyi (1669-1743) joined the riot led by Francis II Rákóczi, it was the German troops turn to attack the fortress of the one who became the enemy.
In the 17th and 18th centuries, the fortress from Carei was the venue of several important diplomatic meetings. Among others, the negotiations for drawing-up and signing the Peace Treaty of Szatmár from 1711 took place here.
Once the military conflicts from the region are settled, the first plans of transformation of the fortress into a building with mostly residential functions appear. Antal Károlyi (1732-1791) is the initiator of these ideas, but the actual transformation works only start off in 1792.
There were 21 rooms on the top floor while on the ground floor there were 20 vaulted rooms. The castle's chapel was attached to the south-eastern side, while the kitchen and other dwelling annexes were built in line with the southern side of the main building.
Some of the most important moments of the history of the baroque castle are the visits paid by the members of the imperial family. Thus, in 1797, József Károlyi (1768-1803) hosted Archduke Joseph de Habsburg at his residency and almost a century later, in 1884, Prince Rudolf de Habsburg spends two days in Carei together with his wife.
A new transformation of the castle, the one that gives the building the current appearance, takes place between 1894-1896, and it is initiated by István Károlyi (1845-1907). Based on the designs of architect Arthur Meinig, the baroque castle is transformed in a construction of eclectic style, with historicist elements, giving the feel of a medieval knight's castle.
Following the death of István Károlyi, in 1907, the members of the family no longer live in Carei. In the chaos created by the events occurred at the end of 1918, many pieces of furniture and valuable objects from inside the castle have disappeared.
A memorable moment in the history of the castle and of Carei in the contemporary period remains the visit of King Ferdinand I of Romania and his wife, Queen Maria, in 1919.
In the interwar period, a wing of the castle is turned into a sanatorium while the rest of it becomes a casino. During the Second World War, with the consent of the Károlyi family a military school is run here, later transformed in a military hospital in 1944. In the communist period, the castle accommodates cultural institutions of public interest: the museum, the cultural center, the municipal library.
Today, the castle is displaying a furniture exhibition, recreating the ambiance of historical times and a local history exhibition.