The terminal is part of a £20m strategy launched by airport operator BAA today to cope with the influx of athletes and spectators for London 2012.
Heathrow predicted August 13 would be its busiest day ever, with 138,000 passengers – 45% more than usual.
Enabling works are currently underway and Mace will oversee the start of construction proper at the end of February with a completion date target of May 30.
BAA is renting the temporary structure from specialist De Boer.
A spokesman told the Enquirer: “Mace are the main contractor on the job and will be subcontracting out the work to a variety of companies.
“The actual terminal structure has been rented from De Boer.”
The Games Terminal will operate on 13-15 August to handle the surge of departing athletes.
It is expected to divert up to 10,100 people and 37,900 bags from other terminals.
The terminal will be built on an area currently used for staff car parking on the south side of the airport.
The 70m x 55m structure will contain 31 check-in desks and be dismantled after the games.
No flights will leave from there, with athletes bussed to departure lounges.
The airport’s head of Olympic and Paralympic planning, Nick Cole, said: “Every part of the airport is working together to ensure we can give the athletes a warm welcome and ensure all passengers enjoy the atmosphere.”