Exeter was the son of Henry Cecil, 1st Marquess of Exeter, and Sarah Hoggins, and succeeded his father ine the marquessate in 1804 at the age of eight. He later held office in the first two Tory administrations of the Earl of Derby as Lord Chamberlain of the Household in 1852 and as Lord Steward of the Household from 1858 to 1859. Apart from his political career he was also Lord Lieutenant of Rutland between 1826 and 1867 and of Northamptonshire between 1842 and 1867. He was made a Knight of the Garter in 1827 and admitted to the Privy Council in 1841.
Lord Exeter died in January 1867, aged 71, and was succeeded in his titles by his only son William. Lady Exeter died in 1879.