[6] One famous member of the family who occasionally resided in Leinster House was Lord Edward FitzGerald, who became involved with Irish nationalism during the 1798 Rebellion, which cost him his life.

Plans were made to turn Royal Hospital Kilmainham, an eighteenth-century former soldiers' home in extensive parklands, into a full-time Parliament House.

However, as it was still under the control of the British Army, who had yet to withdraw from it, and the new Governor-General of the Irish Free State was due to deliver the Speech from the Throne opening parliament within weeks, Michael Collins decided to hire the Leinster House complex for use from September 1922 as a temporary Dáil chamber as it housed a large lecture theatre that could easily be adapted to the needs of the Oireachtas.

Among the world leaders who have visited Leinster House to address joint sessions of the Oireachtas are U.S. presidents John F. Kennedy, Ronald Reagan and Bill Clinton; British Prime Minister Tony Blair; Australian prime ministers Bob Hawke, Paul Keating, and John Howard; and French President François Mitterrand.

Its Kildare Street frontage used to be dominated by Queen Victoria, a large seated bronze statue by John Hughes, first unveiled by King Edward VII in 1908.

Facing the garden front on its Merrion Square side, stands a large triangular monument commemorating three founding figures of Irish independence, President of Dáil Éireann Arthur Griffith, who died in 1922, Michael Collins, who was shot and killed in an ambush by anti-treaty forces in 1922, and Kevin O'Higgins, the Chairman of the Provisional Government and the Vice-President of the Executive Council (deputy prime minister), who was assassinated in 1927.

The main extensions are: A commissioned report delivered to the Ceann Comhairle's office in 2008 cast serious doubts on the safety of Leinster House without major remedial work.

"[19] The building underwent massive restoration and conservation work from December 2017 until August 2019, during which time the entire original Kildare House section was shielded from the elements under a temporary scaffold and plastic roof.

To ensure consistency in the type of granite used in the repairs, the Office of Public Works opted for stone from Ballyknockan quarry, being the nearest geographical substitute.