According to Gregory of Tours, the Bretons were divided into various regna during the sixth century, of which Domnonia, Cornouaille, and Broweroch are the best known; they had been under Frankish suzerainty during the time of Clovis I. This they had thrown off by the time of Chilperic I, who subdued them and their chief Waroch, at least in the east of Brittany. Guntram, Chilperic's brother, retained his lordship over Waroch and the Brittani formed a Frankish tributary-vassal state through the reign of Dagobert I.
In the Chronicle of Fredegar, a Judicael is named as King of the Bretons at this time. It is highly likely that he was the Domnonian king of Breton tradition. This would indicate that Domnonia had at the time swallowed up Broweroch and Judicael had become a high king. This is probably the reason for his dealings with Dagobert and Eligius. In 635, Dagobert ordered Judicael to come to his palace at Clichy and renew fealty to the king, threatening to invade Brittany otherwise. The Breton king complied and arrived with gifts, but threw insult at Dagobert by refusing to eat at the royal table.
Around 640, he retired to the monastery of Saint John at Gwazel, not far from the monastery of Paimpont which he had founded. After his death, he was buried beside his abbot, Saint Méen, and declared a saint; his feast day is 16 December. He is also said to have been the father of Saints Judoc and Winoc.