In 597, reputedly because before he became Pope he had seen English boys for sale in Rome and been so impressed with their blond beauty that he had exclaimed they were non Anglii, sed angeli! ("not Angles, but angels!"), Pope Gregory the Great sent a mission to the English under the leadership of Augustine, the prior of his own monastery of St. Andrew on the Cœlian Hill (who would later become St. Augustine of Canterbury). They went initially to Kent, where King Æþelberht had married Bertha, daughter of the Frankish King Charibert, and a bishop who had accompanied her was in residence. Æþelberht was nonetheless deeply suspicious of Xianity and insisted on meeting the monks in the open air as protection from magic. He became an ally, and by Augustine's death (in a year between 604 and 609) the church had made a good start in southern England. There was a heathen rebellion in Kent and Essex, but the bishops stood firm.

King Sigeberht of East Anglia had lived in exile in Gaul and been baptized there; he requested a bishop from the archbishop of Canterbury and received a Burgundian named Felix who had already volunteered to assist the mission. Ultimately it was the East Anglians who cemented the conversion of Wessex: King Cynegils' conversion had not persuaded his family to follow suit, and his son Cenwalh only accepted baptism when he was exiled at the court of King Anna of East Anglia after 645.

In 625 Edwin, King of Northumbria, married Æþelberg, Æþelberht's daughter, promising to respect her religion and to consider changing his own. Paulinus, a member of Augustine's original mission, was therefore consecrated a bishop and accompanied her north; Edwin received baptism when he recalled a youthful vision that he must obey a stranger to repay having been saved from a dangerous situation as a youth. According to Bede, after making the decision he summoned his counselors and asked them to be baptized with him, whereupon his "chief priest," Coifi, blaming the gods for having rewarded him disproportionately little, repudiated heathenry and desecrated his own temple and another advisor compared human life to the flight of a sparrow in one side of the roof of a hall and out the other. In short, the king's decision to convert was followed by his advisors'. Edwin was baptized on Easter Eve, 627 in a church that he had erected for the occasion and Xianity began to spread rapidly in the North, and Pope Honorius I wrote in 634 giving permission for the establishment of a second archbishopric at York; but Edwin had been dead and Paulinus a fugitive for 20 months by the time the letters were written.

Augustine was unable to get along with the churchmen of Wales, perhaps because their ascetic tradition and his big-city ease were at odds, but also undoubtedly because of some serious differences between Celtic Xianity and Rome - including the date of Easter, the relative power of bishops and abbots, the ceremony of consecration, and the style of the tonsure. But the church in East Anglia benefited greatly from King Sigeberht's hospitality to an eminent Irish hermit, Fursa, and it was Irish monks from Iona, under the leadership of Aidan, who re-established Xianity in the North. They founded the monastery of Lindisfarne, where Aidan died in 651, and are to be thanked for the powerhouse that the church became in Northumbria, with the monasteries of Wearmouth and Jarrow.