He was elected unopposed as a Sinn Féin MP for the Carlow constituency at the 1918 general election. In January 1919, Sinn Féin MPs refused to recognise the Parliament of the United Kingdom and instead assembled at the Mansion House in Dublin as a revolutionary parliament called Dáil Éireann, though Lennon did not attend as he was in prison.
He again elected unopposed for the Carlow–Kilkenny constituency at the 1921 elections. He opposed the Anglo-Irish Treaty and voted against it. He stood unsuccessfully as an anti-Treaty Sinn Féin candidate at the 1922 general election.
- "Mr. James Lennon". Oireachtas Members Database. Retrieved 10 April 2009.
- "Roll call of the first sitting of the First Dáil". Dáil Éireann Historical Debates (in Irish). 21 January 1919. Retrieved 29 March 2008.
- "James Lennon". ElectionsIreland.org. Retrieved 10 April 2009.
Lua error in package.lua at line 80: module 'Module:Buffer' not found.