Ireland's line-up of Major Champions for the event at Carton House, in Co Kildare, at the end of June is now complete.
Clarke and McDowell will join Padraig Harrington, Carton House's Touring Professional Shane Lowry and fellow Northerner Rory McIlroy on the team.
The last time the Irish Open was played at Carton House was in 2006. Then, Clarke, who went on to become the 2011 Open Champion, was third behind winner Thomas Björn.
The Co Tyrone man was also joint runner up to Colin Montgomerie at Fota Island, Co Cork in 2001. This year will mark his 22nd appearance at the event.
Clarke told the European tour's official website: "The Irish Open is obviously one of the highlights of the year for us, and it is always an event I always look forward to playing in.
"The atmosphere at Royal Portrush last year was unbelievable and I think we can expect some more fantastic home support at Carton House."
He continued, saying that he played well in 2006 and hopes to play well again this year.
Meanwhile, Portrush's Graeme McDowell has yet to finish in the top ten in the Irish Open.
Only last week he reached the quarter-finals of the blizzard hit WGC-Accenture Match Play in Arizona, but his best performance at the Irish Open was sharing 11th place at Co Louth in 2004.
Last year, he finished up in a lower position - tied at 16th - despite playing at his home course of Royal Portrush.
"Carton House should be another great venue for the Irish Open," McDowell said, also speaking to the official European tour website.
"Obviously Portrush was a huge success last year and was very special for me personally, but I think the Irish golf fans will again support the event and it will be another celebration of Irish golf.
"Personally, I'd love to win the Irish Open one day and hopefully this can be the year I do it."