Edbald was the son of Aethelbert I of Kent and his wife, Bertha, the daughter of King Caribert I of Paris. He was still a pagan when he succeeded to his father's throne in AD 616, despite the conversion of the latter to Christianity, along with a large portion of the Royal Court, nineteen years before. In accordance with pre-Christian tradition, therefore, he immediately married his father's widow, a lady of unknown name whom King Aethelbert had married sometime after Bertha's death in AD 612. Stripped of its Royal support, the Christian mission in Kent almost collapsed. However, Archbishop Laurence of Canterbury managed to win the new King over and he eventually accepted conversion.

Unfortunately, Kent lost some ground to the other southern Saxon kingdoms during Edbald's reign. The pagan successors of King Saebert of Essex prevented him from restoring St. Mellitus to his London bishopric and the Bretwaldaship was taken up by King Redwald to East Anglia. After the latter's death, however, the Northumbrian King Edwin was in the ascendant and, in AD 625, Edbald entered into a mutually advantageous pact with this now powerful king. To seal the alliance, Edwin married Edbald's sister, Ethelburga, who was to become a central figure in the conversion of the North. Thus Edbald managed to preserve Kent's independence. After Edwin's violent death in AD 633, however, King Oswald, from the rival house of Bernicia, took over in Northumbria and relations had to be renegotiated. Queen Ethelburga and her daughters returned to Kent, but she did not trust her brother with the lives of her sons and little Wuscfrea, and Edwin's eldest grandson, Yffi son of Osfrith, were sent for schooling at the court of her friend, King Dagobert of the Franks. King Edbald restored the Northumbrian alliance by marrying his eldest son, Ermenred, to a Northumbrian princess named Oslava.

By his step-mother, Edbald had one daughter, Mildred. He later married Emma (or Ymme) the daughter of the Merovingian King Theudebert II of Austrasia. She bore him, Ermenred and the King's eventual successor, Erconbert, as well as St. Enswith. King Edbald died in AD 640.