He initially attended the Royal Grammar School, Guildford, before at an early age moving to Magdalen College School at Oxford.
Subsequently he joined Merton College, where he was admitted to a fellowship in 1529 after graduating Bachelor of Arts (24 July 1528). He was an adept in the composition of Latin epigrams. He took holy orders in 1532, and proceeded Master of Arts 19 February 1533.
When, in 1543, Henry VIII and Queen Catherine Parr visited Oxford, Parkhurst wrote Latin verses in their honour and became chaplain to the queen.
Soon afterwards he was appointed rector of Pimperne, Dorset, and in 1549 was presented by Thomas Seymour, 1st Baron Seymour of Sudeley to the living of Cleeve Episcopi, Gloucestershire. Jewel and other Oxford scholars often visited him there.
When Jewel gave humanity lectures at Corpus Christi College, Oxford, Parkhurst went over to hear him, and declared in a Latin epigram that he was metamorphosed from a tutor into a pupil. On the accession of Queen Mary he left the country and settled at Zurich, where he was received by Rudolf Gwalther and other Calvinists.
Returning on the accession of Elizabeth I, on 13 April 1560 he was elected bishop of Norwich, and was consecrated and installed in September following.
He was created Doctor of Divinity at Oxford in 1566. In the see of Norwich, at the time of Parkhurst"s appointment, many of the livings were without incumbents. He did nothing to discourage "prophesyings" in his diocese, and took measures against Catholics.
Defrauded by a servant, Parkhurst moved from the bishop"s palace, which he had repaired, to a small house at Ludham.
And introduced a bill into parliament to prevent such abuses, which was accepted by the government. He died on 2 February 1575, aged 63, and was buried in the nave of his cathedral on the south side.
Parkhurst married Margaret, daughter of Thomas Garnish of Kenton, Suffolk, but left no issue.