Sir Thomas sat as a Member of Parliament in the Irish House of Commons for Carysfort between 1776 and 1797 and served as High Sheriff of County Waterford in 1795, having succeeded to the baronetcy upon his father's death in 1783.
Marriage and issue
Osborne married on 6 April 1816 at St. Margaret's Church, Rochester, Kent, Catherine Rebecca Smith (1796 - 10 October 1856). Catherine Rebecca Smith was the daughter of Major Robert Smith RM (1754 - Chatham, Kent, 2 July 1813) and his wife Margaret Ramsay (1766 - Newtown, Ireland, April 1839), and a granddaughter of the Revd James Ramsay and his wife Rebecca Akers.
Sir Thomas and Lady Osborne had two children:
- Sir William Osborne, 10th Baronet (1817 - 23 May 1824), succeeded in the baronetcy on 3 June 1821
- Catherine Isabella Osborne (30 June 1819 - 20/1 June 1880), married on 20 August 1844 Ralph Bernal Osborne (26 March 1808 - 4 January 1882), and had two daughters.