Gregory was son of a Roman senator and when still in his thirties rose to be praetor and could well have gone to the top as a praetorian prefect. His grandfather had become Felix III, pope 483-92 in the early years of the long Acacian Schism with Constantinople. Three of his father's sisters had become nuns, one of the three abandoning the religious life, marrying the steward of her property and failing to find happiness (Hom. Evang. 38. 15; Dial. 4. 17). He aspired to be a monk and founded his own monastery of St Andrew in Rome. Self-discipline and humility were basic virtues in the ascetic life. It is not clear that his monastery used the Rule drafted by Benedict of Nursia as a 'little rule for beginners', considerably mitigating an earlier and more strenuous 'Rule of the Master'; but when Cassino was destroyed in 585 and the monks took refuge in Rome, Gregory had informants to brief him for a biography of Benedict which was to be the second of the four books of his Dialogues.
Pope Pelagius II ordained him to be deacon and sent him to Constantinople as apocrisiary; it was normal for apocrisiaries to the court and the patriarch to be in deacon's orders, and they were officially accredited to convey documents from emperor to pope and vice versa. Gregory held this post for six years, 579-85. During this time he appears not to have learnt Greek, so he probably had a local translator. 1 At this time it would be easier to find a civil servant in Constantinople with a legal training and therefore some grasp of Latin (John Lydus could be an example) than to find a Latin-speaker in Italy capable of fluency in Greek. His residence in Constantinople brought him into contact with influential people, and among those he met there was Leander bishop of Seville for whom he wrote his commentary on Job, carefully expounding the text as one in which 'lambs could paddle and elephants swim'. Gregory's preaching was profoundly biblical, allowing for both a literal or moral sense and for an allegorical inner meaning.