Thomas Dundas, second Earl of Zetland, was born in Marylebone, London on 5 February 1795. He was the son of Lawrence Dundas, first Earl of Zetland and his wife Harriet, the daughter of General John Gale. Dundas was educated at Harrow School, Middlesex and Trinity College, Cambridge, where he was awarded a Master of Arts degree in 1815.
He was elected Whig Member of Parliament for Richmond, Yorkshire in 1818, serving until 1830 and in 1835 serving until 1839. He also served as Member of Parliament for York from 1830 to 1832 and from 1833 to 1834. He married Sophia Jane, the daughter of Sir Hedworth Williamson, sixth Baronet of East Markham, Nottinghamshire, on 6 September 1823, however the couple remained childless. He succeeded his father as second Earl of Zetland in February 1839. He was appointed Lord Lieutenant and Custos Rotulorum of the North Riding of Yorkshire in 1839, serving until his death. He was installed as a Knight of the Order of the Thistle in 1861.
He resigned the Order on being made a Knight of the Order of the Garter in 1872. He was initiated as a freemason in Prince of Wales’s Lodge, No. 259 [SN 1097], London on 18 June 1830, where he served as Deputy Worshipful Master from 1837 to 1838. He became a joining member of Lodge of Antiquity, No. 2 [SN 1], London in May 1839, resigning in 1847 having been elected an Honorary member, First Class; Royal Alpha Lodge, No. 16 [SN 37], London on 17 June 1843, where he served as Worshipful Master in 1843, 1848, 1854, 1859, 1863, 1866 and 1868. He served as Provincial Grand Master, Yorkshire North and East Riding from 1839 to 1870. He was appointed Junior Grand Warden by the United Grand Lodge of England in 1832.
He was promoted to Deputy Grand Master in 1839; Pro Grand Master in 1840 and Grand Master in 1844, serving until 1870. In Royal Arch he was exalted in Prince of Wales’s Chapter, No. 493 (now No. 259) on 1 June 1832. He served as Grand Superintendent, Yorkshire North and East Riding from 1839 to 1873. He was appointed Second Grand Principal by the Supreme Grand Chapter of Royal Arch Masons of England in 1839.
He was promoted to Pro First Grand Principal in 1841 and First Grand Principal in 1844, serving until 1870. He died at Aske Hall, Yorkshire aged seventy-eight on 6 May 1873. His probate record states his residences as Aske, Richmond and Marske Hall, Guisborough, both in Yorkshire and 19 Arlington Street, London.