[2] He was made deacon on 23 April 1758, by John Thomas (Bishop of Salisbury) at his palace;[3] and ordained priest on 24 December 1758 by Frederick Cornwallis, Bishop of Lichfield and Coventry, at Grosvenor Chapel (on letters dimissory from Salisbury).

[4] He became Rector of Street, Somerset (1769–1770), of Stanhope, County Durham (1770–1771), Master of the Temple in 1772, Dean of Rochester (1775–1779), Bishop of Lincoln in 1779, additionally Dean of St Paul's in commendam in 1782, and was Bishop of Durham from 1787 until his death.

[1][2][5] His election to Lincoln was confirmed on 29 May 1779 (at St Mary-le-Bow)[6] and he was consecrated a bishop on 30 May 1779 by Cornwallis (then Archbishop of Canterbury) at Lambeth Palace;[7] he was translated to Durham on 10 March 1787, by the confirmation of his election at St Mary-le-Bow.

Thurlow had suffered from some time from a bowel complaint, which he initially thought was the result of piles.

He consulted John Hunter after a number of other physicians and surgeons had failed to provide him with a satisfactory diagnosis.