After having consented to leave to his younger brother Charibert the kingdom of Aquitania, he retook it by force in 631, at the death of Charibert, seizing at the same time his treasures, and causing or permitting to be murdered his young nephew Chilperic, rightful heir of his father.

About the same time Dagobert had assigned amongst the Bavarians, subjects of his beyond the Rhine, an asylum to nine thousand Bulgarians, who had been driven with their wives and children from Pannonia.

Not knowing, afterwards, where to put or how to feed these refugees, he ordered them all to be massacred in one night; and scarcely seven hundred of them succeeded in escaping by flight.

The private morals of Dagobert were not more scrupulous than his public acts.
"A slave to incontinence as King Solomon was," says his biographer Fredegaire, "he had three queens and a host of concubines." Given up to extravagance and pomp, it pleased him to imitate the magnificence of the imperial court at Constantinople, and at one time he laid hands for that purpose, upon the possessions of certain of his "leudes" or of certain churches; at another he gave to his favorite church, the Abbey of St.
Denis, "so many precious stones, articles of value, and domains in various places, that all the world," says Fredegaire, "was stricken with admiration." But, despite of these excesses and scandals, Dagobert was the most wisely energetic, the least cruel in feeling, the most prudent in enterprise, and the most capable of governing with some little regularity and effectiveness, of all the kings furnished, since Clovis, by the Merovingian race.

He had, on ascending the throne, this immense advantage, that the three Frankish dominions, Austrasia, Neustria, and Burgundy were re-united under his sway; and at the death of his brother Charibert, he added thereto Aquitania.