He was the nephew of King Æthelberht of Kent and was converted to Christianity in 604. He was baptised by Saint Mellitus, Bishop of London but his sons remained pagan, and after his death they drove Melitus from London.
He was the son of Sledda. By tradition he was buried in Westminster Abbey, which he supposedly founded; a tomb said to be his (also that of his consort Ethelgoda) is located in the South Quire. However, on the evidence of dating of the artefacts, the tomb, found in Prittlewell in the autumn of 2003 may be the burial chamber of Saebert. Several foil crosses, perhaps sewn into his shroud, correlate with the accepted history that Saebert was a convert to Christianity. Other funereal goods, such as glass and copper alloy bowls, indicate a continuation of pagan beliefs.