Of noble birth, he is first recorded as the abbot of Lyminge, from where he was elevated to the see of Hereford in 736. He served in that capacity for four years before his elevation to the see of Canterbury in 740. While bishop, he composed an epitaph for the tomb of his three predecessors at Hereford. The cathedral church of the see may not even have been located at Hereford by Cuthbert's time.
The identification of the Cuthbert who was bishop of Hereford with the Cuthbert who became archbishop, however, comes from Florence of Worcester and other post-Conquest sources. The conetemporary record in the Anglo-Saxon Chronicle says that Cuthbert was consecrated archbishop, where if he had been bishop of Hereford, he would have been translated. No consecration is needed when a bishop is translated from one see to another. Given the nature of the sources, the identification of the bishop of Hereford with the archbishop of Canterbury, while likely, must not be regarded as proven.
Cuthbert was the recipient of a long letter from Saint Boniface, who complained about the lax morals of the clergy in the British Isles, and too much drinking of alcohol by the Anglo-Saxon bishops. He also sent letters to Lull who was archbishop of Mainz and a native of England. During Cuthbert's time as archbishop he no longer claimed authority over all of Britain, like his predecessor Theodore. Pope Gregory III in 735 had sent a pallium to the bishop of York, raising the see of York to the status of an archbishopric. As a sign of the enhanced status of York, Cuthbert only consecrated bishops south of the Humber River and his synods were attended only by bishops from the south of England.
He presided over the Council of Clovesho in 747 along with Æthelbald, King of Mercia. This gathering mandated that all clergy should explain the basic tenets of Christianity to the laity. Cuthbert sent his deacon Cynebert to Pope Gregory III after the council with a report on the council and its resolutions. This action may have been taken in response to Boniface's complaints about Cuthbert and Æthelbald to the papacy. The actions of the council were also gathered into a collection at Cuthbert's command.
After the council, Cuthbert continued to correspond with Boniface up until Boniface's martyrdom in 754, and then sent condolences to Boniface's successor. Cuthbert held a second synod in 758, but nothing is known of any enactments it made. He also built the church of St. John the Baptist in Canterbury, which was destroyed by fire in 1067. He was buried in his new church. The new church was located on the west side of the cathedral, and was used as a baptistery. The church also became a burial site for many of the archbishops, and later was used for trials by ordeal. There is no explicit contemporary reference that states that these uses were intended by Cuthbert, but the fact that the church was dedicated to St. John the Baptist argues strongly that Cuthbert at least intended the new building as a bapistery.
The burial practices of the archbishops did change after Cuthbert, but it is not clear whether this was intended by Cuthbert, as some Post-Conquest sources have it, or if it was due to some other reasons unconnected with Cuthbert. Some scholars have seen the change in burial customs, which extended over most of Britain, as resulting from a hypothetical council held by Cuthbert that mandated burial in church yards, instead of outside the city limits as had been the custom previously. However, the main evidence for this theory is a 16th century tradition at Canterbury and the archealogical evidence of a change in burial patterns. Although a change did occur, the archealogical evidence does not give a reason why this change happened, and given the late date of the Canterbury tradition, the theory cannot be considered proven.
He died on 26 October 760 and was later canonized with a feast day of 26 October. He was buried in his church of St. John, and was the first Archbishop of Canterbury that was not buried in St. Augustine's. His letters to the Anglo-Saxon missionaries on the European Continent show him to have been highly educated.