[4] Mordecai was educated at the bluecoat charity school, Christ's Hospital, entering on 13 July 1695,[5] not as an orphan, but on the gift of John Phillips, cook, who left a gift specifically for two "poor children of such poor members of the company of cooks as by the master and wardens of the said company should from time to time be presented".

[8] In 1709, Dr Richard Bentley, classical scholar and Master of Trinity College, Cambridge, applied to the Governors of Christ's Hospital for Mordecai to travel abroad under the tutelage of older graduate, Mr James Jurin (1684–1750), as being "the best way for their improvement and rising in the world".

They travelled to Leyden, one of the most important centres for the study of medicine and natural Philosophy during the eighteenth century to attend the lectures of Hermann Boerhaave.

He received his Doctor of Divinity at Lambeth Palace in London, by William Wake, Archbishop of Canterbury; his patent bears the date 22 March 1731.

On 1 April 1732 in St Anne's Church, Dublin, Dr Mordecai Cary was consecrated Bishop of Clonfert, County Galway, which position he held to 1838.

[11] Clonfert was the abbey and cathedral founded by St Brendan "the Navigator" in about 557, and its school became one of the most famous and largest in western Ireland.

[13] On 27 September 1735 the Dublin Gazette read: "On Wednesday last arrived here the Duke and Duchess of Dorset with the Rt Hon.

On this visit by the Duke, "1735-6 Mordecai Cary DD Bishop of Clonfert, was translated to the Sees by patent dated December 20th and was enthroned by proxy at Achonry on March 19th and at Killala next day".