Sir Thomas Hoby was the second son of William Hoby of Leominster in Herefordshire, by his second wife, Katherine the daughter of John Vaughan. He matriculated at Cambridge, to St. John's College, in 1545. It is sometimes asserted that he also spent some time at Oxford. He subsequently visited France, Italy and other foreign countries and “was many ways well furnished with learning and very expert in knowledge of divers tongues”.

By his marriage, on 27th June 1558, to Elizabeth, third daughter of Sir Anthony Cooke, of Gidea Hall in Essex, he had two sons, Edward and Thomas Posthumus (both subsequently knighted), and two daughters, Elizabeth and Anne, who died within a few days of each other in February 1571.

On 9th March 1566, Thomas was knighted at Greenwich (Kent) and was sent as Ambassador to France at the end of the same month. At the time of his landing in Calais Haven, on 9th April, a soldier at the town gate shot through the English flag in two places. Hoby demanded redress for the insult and obtained it, after some delay, but he was not permitted to view the new fortifications.

He died in Paris on 13th July 1566 and was buried in the church of Bisham in Berkshire, a manor he had inherited from his half-brother, Sir Philip, in 1558. His widow erected a superb renaissance-style monument to the two there, and probably brought sculptors from France to carve the white marble effigies in complete armour.

Hoby was author of several transla­tions, including 'The Gratulation of.…M. Martin Bucer....unto the church of England for the restitution of Christ’s Religion, and his Answer unto the two railing epistles of Steven, Bishop of Winchester, concerning the unmarried state of priests and cloisterers,' (1549) and 'The Courtier of Count Baldessar Castilio, divided into four books' (1561). He also left a manuscript diary.