Thomas was the child of Sir Richard Elyot's first marriage with Alice De la Mare, but neither the date nor place of his birth is accurately known.

Elyot, in a letter addressed to Thomas Cromwell, says that he never received the emoluments of this office, while the empty honour of knighthood conferred on him when he was displaced in 1530 merely put him to further expense.

As ambassador Elyot had been involved in ruinous expense, and on his return he wrote unsuccessfully to Cromwell begging to be excused, on the grounds of his poverty, from serving as High Sheriff of Cambridgeshire and Huntingdonshire for 1532.

[3] The story of an earlier embassy to Rome (1532), mentioned by Burnet, rests on a late endorsement of instructions dated from that year, which cannot be regarded as authoritative.

[citation needed] In 1531 he produced The Boke named the Governour, dedicated to King Henry VIII which was printed by Thomas Berthelet (1531, 1534, 1536, 1544, etc.).

Elyot expressly acknowledges his obligations to Erasmus's Institutio Principis Christiani but he makes no reference to the De regno et regis institutione of Francesco Patrizzi (died 1494), bishop of Gaeta, on which his work was undoubtedly modelled.

In 1536 he published The Castel of Helth, a popular treatise on medicine, intended to place a scientific knowledge of the art within the reach of those unacquainted with Greek.

[2] He was violently attacked by Humphrey Hody and later by William Wotton for putting forward a pseudo-translation but Henry Herbert Stephen Croft (1842–1923) later discovered that there was a Neapolitan gentleman at that time bearing the name of Poderico, or, Latinized, Pudericus, with whom Elyot may well have been acquainted.

Roger Ascham mentions his De rebus memorabilibus Angliae and William Webbe quotes a few lines of a lost translation of the Ars Poetica of Horace.