[2] When his father was assassinated in 575 by two slaves of Queen-consort Fredegund of Soissons,[3] Childebert was taken from Paris by Gundobald (according to one story, after being lowered from a window in a bag by his mother[4]), one of his faithful lords, to Metz (the Austrasian capital), where he was recognized as sovereign.

With the assassination of Chilperic in 584 and the dangers occasioned to the French monarchy by the expedition of Gundoald in 585, Childebert threw himself unreservedly to the side of Guntram.

By the Treaty of Andelot of 587, Childebert was recognised as Guntram's heir,[6] and with his uncle's help in 587 he quelled the revolt of Dukes Rauching, Ursio, and Berthefried, and succeeded in seizing the castle of Woëvre.

Many attempts were made on his life by Fredegund, wife of Chilperic, who was anxious to secure Guntram's inheritance for her son Clotaire II.

[8] On the death of Guntram in 592, Childebert annexed the kingdom of Burgundy,[9] and even contemplated seizing Clotaire's estates and becoming sole king of the Franks.