The company said it had placed firm orders for 20 of the double-decker aircraft with options for a further 16. Deliveries are scheduled to start in 2020.
The deal was expected to be signed during the Dubai Airshow in November but was delayed without any explanation amid reports of tough negotiations.
Airbus's decision in 2007 to pursue the A380, capable of packing in 853 seats, was diametrically opposed to Boeing's bet on the Dreamliner, marketed as a more efficient plane that could be used for both medium and long-distance flights.
But the economics of the A380 have proved daunting, with airlines having to fly every flight at full capacity in order to make a profit.
Airbus warned on Monday that it might have to end production of the A380, having booked no new orders for the plane in two years.
It said it regarded Emirates as the only airline with the capacity to place an order of the size required to keep production going.
"Our customers love it, and we've been able to deploy it on different missions across our network, giving us flexibility in terms of range and passenger mix."
Emirates operates a fleet of 269 wide-bodied aircraft and flies to 157 destinations.