Born in Cambridge on 5 May 1542, the eldest son of William Cecil, first Baron Burghley (1520/21–1598), and his first wife, Mary (c.1520–1544).
Educated at home by tutors
Matriculated Fellow-Commoner from Trinity, Michaelmas 1558
M.A. 1571
Admitted at Gray's Inn
In 1561 Thomas's father sent him abroad to complete his education. Once he reached Paris he began to enjoy life and neglect his studies. His father accused him of being 'slothful in keeping his bed, rash in expenses, careless in his apparel, an unordinate lover of dice and cards; in study soon weary, in game never'. He seems to have amended his ways and completed his grand tour by visiting Antwerp, Speyer, Heidelberg, and Frankfurt, before returning home early in 1563 after an absence of nearly two years.
In 1564 he married Dorothy Neville, daughter of Lord Latimer of Belvoir Castle. They had thirteen children, five sons and eight daughters. Dorothy died in 1609 and a year later Cecil married Frances Smith, a thirty-year-old widow, less than half his age and younger than almost all his children. They had one daughter, who died in infancy.
He was MP for Stamford, Lincolnshire, in 1562, 1571, 1572; for Lincolnshire, 1584-86; for Northamptonshire in 1592
In 1569 he helped to suppress the revolt of the northern earls.
In 1573 he volunteered to help the Scottish regent, Morton, storm Edinburgh Castle.
In 1575 he was knighted by the queen during a tournament at Kenilworth.
In 1585 when the Earl of Leicester was sent with an army to help the Dutch, Thomas Cecil was made captain of horse and governor of the English-controlled port of Brill, although he soon resigned on grounds of ill health.
In July 1588, when the Spanish Armada invaded he was made colonel in an army set up to defend 'Her Majesty's person'.
In 1601 as colonel-general of the London foot he helped his half-brother Robert Cecil smash the rebellion of the Earl of Essex.
In 1590 he had become the lord of the manor of Wimbledon and there built an impressive mansion. Over the next 10 years he entertained the Queen here on several occasions.
He was given a commission as Lord President of York (or President of the Council of the North) with special orders to hunt down Catholic recusants.
In 1598 on the death of his father he became second Baron Burghley.
For his part in crushing the Essex revolt he received the Garter.
When James I became king, he was first made a member of the Privy Council.
In 1605 he was made Earl of Exeter, at the same time as Robert was created Earl of Salisbury.
In 1617 his wife Frances was accused of plotting to poison Lady Lake, wife of one of the secretaries of state. The scandal became the talk of London. It was a very complicated affair, and the evidence was said to fill 17,000 sheets of paper. The Earl appealed to the King, who took such an interest in the case that he presided in person in Star Chamber and then went down to Wimbledon to test the chief witnesses. Finally he pronounced the Countess innocent and sentenced Lady Lake and her husband to the Tower for life.
Cecil died, probably at Wimbledon, on 7 February 1623.