During the G8 Summit, being held at Lough Erne golf resort in Northern Ireland on 17-18 June, G4S will bring in 450 staff to supplement the police.
The G4S team will deliver security including stewarding, monitoring of site perimeters and securing access to venues.
Meanwhile, the PSNI has drafted in a further 3,600 police officers from Britain to help support the event, which will be policed by a total of around 5,000 officers.
This is the first time the G8 Summit has been held in the UK since 2005, when it was hosted by Gleneagles, in Scotland, and included security from G4S.
Eric Alexander, managing director of G4S Events, said: "We are delighted to have been awarded this contract and be given the opportunity to use our proven expertise to help the PSNI secure this extremely high-profile event."
The event will be hosted by Prime Minister David Cameron, and brings together the eight wealthiest nations to address global issues.
Research carried out by Barclays shows that the G8 event could boost business in the area by £40m, with companies in the tourism and hospitality industry showing the most positive reaction to its potential effects.
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