The firm behind the Olympics security shambles is one of two chosen to support the PSNI at the G8 Summit next month.
G4S will supply 450 employees to the event at Lough Erne golf resort in June – despite suffering a multi-million pound loss and damage to its reputation after failing to provide all of its contracted guards to the London Games last year.
It will work in tandem with Eventsec, Northern Ireland's biggest private security company, which provided staff for the MTV European Music Awards in Belfast in 2011 as well as the Balmoral Show.
Secretary of State Theresa Villiers also said additional military personnel and 3,600 police officers from across Britain will assist the PSNI during the G8 on June 17 and 18, when the leaders of the world's eight wealthiest countries are expected in Fermanagh.
It will be the first time the annual summit has been held in the UK since it was at Gleneagles in Scotland in 2005.
G4S caused controversy at the London 2012 Olympics when it failed to provide all 10,400 security guards needed for the £284m contract, forcing the military to step in.
The fiasco left the company with losses of £88m and its chief executive, Nick Buckles, told MPs the Olympics failure was a "humiliating shambles for the company''.
Speaking at a press conference at Hillsborough Castle yesterday, Ms Villiers said that lessons had been learned and claimed that the UK Foreign Office was confident the firm could deliver.
"The G8 is considerably less than the numbers that were required for the mammoth operation at the Olympics," she added.
"One of the reasons why we are working with two partners in this instance, not just G4S but Eventsec as well, was to build in further resilience."
A total of 3,600 police officers from forces in England, Scotland and Wales are being drafted into Northern Ireland to bolster the 7,500 from the PSNI.
They are being deployed as part of a mutual aid scheme and will be used for public order policing as well as providing specialist support such as dog handling and maritime security.
Chief Constable Matt Baggott said it was the biggest policing operation the PSNI had ever undertaken. "The very scale of the 3,600 is an indication of our thorough preparation to make the summit safe and secure," he said.
G4S – which has previously provided support to the 2005 G8 Summit in Gleneagles and the G20 Summit in London – said its staff will provide stewarding, monitoring of site perimeters and securing access to venues.
Ms Villiers declined to divulge how many extra troops would be deployed to Fermanagh for the two-day summit next month but said military assistance would be used to back-up the police.
She said that army helicopters will be used to fly world leaders and their entourages to and from the event outside Enniskillen.
Meanwhile, assistant chief constable Alistair Finlay, said: "I am comfortable with the structures that we have put in."