The eldest son of William Parker, he was born in Norwich, in St Saviour's parish. His mother's maiden name was Alice Monins and she may have been related by marriage to Thomas Cranmer. When William Parker died, in about 1516, his widow married John Baker. Parker was sent in 1522 to Corpus Christi College, Cambridge, and graduated with a Bachelor of Arts degree in 1525. He was ordained deacon in April 1527 and priest in June the same year. In September 1527 he was elected a fellow of Corpus Christi and began his Master of Arts degree in 1528. He was one of the Cambridge scholars whom Thomas Wolsey wished to transplant to his newly-founded 'Cardinal College' at Oxford.

Parker, like Cranmer, declined Wolsey's invitation. He had come under the influence of the Cambridge reformers, and after Anne Boleyn's recognition as queen he was made her chaplain. Through her, he was appointed dean of the college of secular canons at Stoke-by-Clare in Suffolk in 1535. Hugh Latimer wrote to him in that year urging him not to fall short of the expectations which had been formed of his ability. Shortly before Anne Boleyn's death in 1536, she commended to his care her daughter Elizabeth. In 1537 he was appointed chaplain to King Henry VIII. In 1538 he was threatened with prosecution, but Richard Yngworth, the Bishop of Dover, reported to Thomas Cromwell that Parker "hath ever been of a good judgment and set forth the Word of God after a good manner. For this he suffers some grudge." He graduated DD in that year, and in 1541 was appointed to the second prebend in the reconstituted cathedral church of Ely. In 1544, on Henry VIII's recommendation, he was elected master of Corpus Christi College, and in 1545 vice-chancellor of the university. He got into some trouble with the chancellor, Stephen Gardiner, over a ribald play, Pammachius, performed by the students, which derided the old ecclesiastical system.

Rise to power

On the passing of the Act of Parliament in 1545 enabling the king to dissolve chantries and colleges, Parker was appointed one of the commissioners for Cambridge, and their report may have saved its colleges from destruction. Stoke, however, was dissolved in the following reign, and Parker received a generous pension. He took advantage of the new reign to marry in June 1547, before clerical marriages had been legalised by parliament and convocation, Margaret, daughter of Robert Harlestone, a Norfolk squire. They had initially planned to marry since about 1540 but had waited until it was not a felony for priests to marry. The marriage was a happy one, although Queen Elizabeth's dislike of Margaret was later to cause Parker much distress. During Kett's Rebellion, he preached in the rebels' camp on Mousehold Hill near Norwich, without much effect, and later encouraged his secretary, Alexander Neville, to write his history of the rising.

Parker's association with Protestantism advanced with the times, and he received higher promotion under John Dudley, 1st Duke of Northumberland, than under the moderate Edward Seymour, 1st Duke of Somerset. At Cambridge, he was a friend of Martin Bucer and preached Bucer's funeral sermon in 1551. In 1552 he was promoted to the rich deanery of Lincoln, and in July 1553 he supped with Northumberland at Cambridge, when the duke marched north on his hopeless campaign against the accession of Mary Tudor. As a supporter of Northumberland and a married man, under the new regime Parker was deprived of his deanery, his mastership of Corpus Christi, and his other preferments. However, he survived Mary's reign without leaving the country – a fact that would not have endeared him to the more ardent Protestants who went into exile and idealised those who were martyred by Queen Mary. Parker respected authority, and when his time came he could consistently impose authority on others. He was not eager to assume this task, and made great efforts to avoid promotion to the archbishopric of Canterbury, which Elizabeth designed for him as soon as she had succeeded to the throne.

He was elected on 1 August 1559 but, given the turbulence and executions that had preceded Elizabeth's accession, it was difficult to find the requisite four bishops willing and qualified to consecrate Parker, and not until 19 December was that ceremony performed at Lambeth by William Barlow, formerly Bishop of Bath and Wells, John Scory, formerly Bishop of Chichester, Miles Coverdale, formerly Bishop of Exeter, and John Hodgkins, Bishop of Bedford. The allegation of an indecent consecration in the Nag's Head Fable seems first to have been made by the Jesuit Christopher Holywood in 1604, and has since been discredited. Parker's consecration was, however, legally valid only by the plenitude of the royal supremacy; the Edwardine Ordinal, which was used, had been repealed by Mary Tudor and not re-enacted by the parliament of 1559. Although the Papal Commission which pronounced Anglican Orders "null and void" in 1896 could not dispute that the 'manual' succession, that is, the actual laying on of hands and prayer, had not been broken in as much as two of the four consecrators of Parker, Barlow and Hodgkins, had been ordained with the Roman Pontifical in the Latin Rite in the 1530s, and all of them had been made bishops by bishops who were consecrated with the Roman Pontifical, the Roman Catholic Church asserted in the condemnation of 1896 that "defect of form and intent" of consecration were insufficient to make a bishop, and therefore represented a break in the apostolic succession, but the Church of England has rejected this, arguing that the form of words used made no difference to the substance or validity of the act, and that the words in the Rite itself gave plenty of evidence as to the intent. The Roman Catholic viewpoint stated that the Rite to be valid had to include the intent to make a sacrificing priest. The Anglicans retorted that the only things that ordination rites had in common throughout the history of the Church was the laying on of hands and prayer. In any case Parker was already a 'sacrificing' priest as he had been ordained as such in 1527 in the Lati