Hamilton was the second son of Henry Hamilton, of Bailieborough, county Cavan, and his wife Rebecca Blackwell. 
Hamilton was returned to the Irish Parliament as Member for Carlow in 1725 and sat until 1727. He was then Member for Dundalk from 1728. He was returned as Member of Parliament for Wendover by a considerable majority at a by-election on 18 March 1728, presumably due to his distant cousin Lord Limerick, the other sitting Member. He was consulted by the 1st Lord Egmont on Irish matters in 1731, when he drafted a petition and bill to allow unenumerated commodities to go direct to Ireland from the colonies, instead of through Great Britain. He supported the Government, voting with them on the army in 1732 and the excise bill in 1733. He was proposed as a government candidate for Wendover late in 1733, but did not stand at the 1734 British general election. 
- "The Hamilton Manuscripts". National Library of Scotland. pp. 163–164. Retrieved 15 April 2019.
- "HAMILTON, John (b.bef.1690), of Holmpatrick, co. Dublin". History of Parliament Online. Retrieved 2 January 2019.
|Parliament of Ireland|
| Member of Parliament for Carlow
With: Richard Wolseley
| Member of Parliament for Dundalk
With: Thomas Fortescue
|Parliament of Great Britain|
The Viscount Limerick
| Member of Parliament for Wendover
With: The Viscount Limerick
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