Treacy was born in Ballinasloe, County Galway in 1951. He was educated at Gurteen National School and St. Joseph's College, Garbally Park in Ballinasloe. He worked as an auctioneer and financial services manager before entering public life. He is married to Mary Cloonan and has three daughters and one son.
Treacy was first elected to Dáil Éireann at a by-election in July 1982 caused by the death of Fianna Fáil TD Johnny Callanan and was re-elected at each election until his retirement in 2011. His election marked the last time a government party was successful in winning a by-election until the election of Patrick Nulty of the Labour Party in the Dublin West by-election in 2011. He was a member of Galway County Council from 1985–91.
Over his many years in the Dáil, Treacy has held a number of junior ministerial portfolios. In 1987 Treacy joined the junior ministerial team as Minister of State at the Department of Finance with special responsibility for the Office of Public Works and the Central Development Committee. The following year he became Minister of State at the Department of the Taoiseach. It was in this capacity that Treacy became the State's first Minister for Heritage Affairs.
Between 1989 and 1991 he served as Minister of State for Children at the Department of Health, before being appointed Minister of State at the Department of Justice with responsibility for Law Reform. In 1992 Treacy returned to the Department of Finance again before serving at the Departments of the Taoiseach, Finance, Transport, Energy and Communications during the Fianna Fáil–Labour Party government holding special responsibility for Energy.
Some months after Fianna Fáil's return to power in 1997 Treacy became Minister for Science, Technology and Commerce at the Departments of Enterprise, Trade and Employment and Education and Science replacing Michael Smith who had been promoted to cabinet following the resignation of Ray Burke. Following re-election in 2002 he became Minister of State at the Department of Agriculture and Food, with responsibility for Food and Horticulture.
Following Taoiseach Bertie Ahern's cabinet reshuffle in September 2004, Treacy was appointed Minister of State at the Departments of Foreign Affairs and the Taoiseach, with special responsibility for European Affairs.
Treacy was returned to Dáil Éireann at the 2007 general election. This was his eighth successive time to be elected. However, the manner in which this was achieved is somewhat unusual in Irish politics for it was Treacy's seventh time to be elected at a general election without reaching the necessary quota of votes.
However, following 17 years as a Minister of State in various administrations, Treacy was not reappointed to a junior ministerial post by then Taoiseach Bertie Ahern. He was subsequently appointed Chairman of Joint Oireachtas Committee on the implementation of the Good Friday Agreement.
- "Noel Treacy". Oireachtas Members Database. Retrieved 4 November 2009.
- "Noel Treacy". ElectionsIreland.org. Retrieved 4 November 2009.
- "Fahey left out of junior ministers line-up". The Irish Times. 6 June 2007.
- Carr, Aoife (25 January 2011). "FF's Noel Treacy to stand down". The Irish Times. Retrieved 26 January 2011.