The Gepids' participation in the Huns' campaigns against the Roman Empire brought them much booty, contributing to the development of a rich Gepid aristocracy.^[12] A "countless host" under the command of Ardaric formed the right wing of the army of Attila the Hun in the Battle of the Catalaunian Plains in 451.^[13] On the eve of the main encounter between allied hordes, the Gepids and Franks met each other, the latter fighting for the Romans and the former for the Huns, and seem to have fought one another to a standstill.

Attila the Hun died unexpectedly in 453. Conflicts among his sons developed into a civil war, enabling the subject peoples to rise up in rebellion.^[14] According to Jordanes, the Gepid king, Ardaric, who "became enraged because so many nations were being treated like slaves of the basest condition",^[15] was the first to take up arms against the Huns. The decisive battle was fought at the (unidentified) Nedao River in Pannonia in 454 or 455.^[16] In the battle, the united army of Gepids, Rugii, Sarmatians and Suebi routed the Huns and their allies, including the Ostrogoths.^[17] It was the Gepids who took the lead among the old allies of Attila, and establishing one of the largest and most independent new kingdoms, thus acquiring the "capital of esteem that sustained their kingdom for more than a century".^[18] It covered a large part of the former Roman province of Dacia, north of the Danube, and compared to other Middle Danubian kingdoms it remained relatively un-involved with Rome.

The Gepids were defeated by the Lombards and Avars a century later in 567, when Constantinople gave no support to them. Some Gepids joined the Lombards in their subsequent conquest of Italy, some moved into Roman territory, and other Gepids still lived in the area of the old kingdom after it was conquered by the Avars.