A former Branch Vice-President of the Irish Transport and General Workers Union, Cregan is a long-standing member of Cork City Council, and was Lord Mayor of Cork from 1991 to 1992. He had unsuccessfully contested the Cork South-Central constituency at the 1981 and February 1982 general elections. He stood in the 1982 Seanad elections, winning a seat on the Labour Panel, which he held until his defeat in the 1989 elections to the 19th Seanad Éireann.
He was unsuccessful again when he stood again in Cork South-Central at the 1992 general election, but in the subsequent elections to the 20th Seanad he was re-elected on the Labour Panel. He was re-elected in 1997 to the 21st Seanad, but was narrowly defeated in the 2002 elections to the 22nd Seanad.
In January 2009 he announced his retirement from politics and did not contest the 2009 local elections.
He is well known in Cork for his chain of restaurants called Dino's.
- "Mr Denis (Dino) Cregan". Oireachtas Members Database. Retrieved 12 January 2008.
- "Provosts, Mayors and Lord Mayors of Cork". Cork City Council. Archived from the original on 19 November 2007. Retrieved 12 January 2008.
- "Denis 'Dino' Cregan". ElectionsIreland.org. Retrieved 8 January 2008.
- Ralph Riegel (14 June 2004). "Angry Leesiders turn to the left". Europe Intelligence Wire. Retrieved 12 January 2008.
| Lord Mayor of Cork