Kielty joins a lineup of Rest of the World stars that also includes Hollywood actors Will Ferrell, Mike Myers and Gerard Butler.
Actor Michael Sheen will captain the side for the second year running and Gordon Ramsay will also return.
Sheen's Rest of the World side triumphed over Robbie Williams's England in the 2010 Soccer Aid, winning a dramatic final shoot-out thanks to a Woody Harrelson penalty.
Williams's team this year will include Aston Merrygold and Marvin Humes from JLS, Williams's close friend Jonathan Wilkes, Ben Shephard, Jamie Theakston and X Factor's Olly Murs.
Teddy Sheringham and Edwin van der Sar are the first footballers to sign up for the fundraiser.
Watch the finale of the 2010 Soccer Aid penalty shoot-out featuring Patrick Kielty below:
Previous Soccer Aid matches have raised over £7 million for UNICEF.
David Bull, UNICEF UK executive director, said: "Soccer Aid 2012 will raise vital money to change children's lives around the world. Every minute of every day, children die from easily preventable diseases like diarrhoea and malaria.
"Right now, children are suffering because they don't have enough to eat. It shouldn't be like this. Please, buy a ticket to go to Soccer Aid or watch the match and help us make a change for children."
Tickets for Soccer Aid 2012 are now on sale. Call 0161 444 2012 and visit ITV.com/socceraid or ManUtd.com/socceraid.