The airline has options for up to 100 additional jets, Delta said, ahead of its investor day presentation.
It is also a win for United Technologies unit Pratt & Whitney as the carrier had selected the engine maker to power its new planes.
"This is the right transaction at the right time for our customers, our employees and our shareholders," said Delta CEO Ed Bastian.
The airline said it will start taking deliveries of the plane in 2020.
The Airbus deal is a loss for rival airplane maker Boeing whose new 737 planes compete with the European plane makers' model.
A Boeing spokesman said, "Delta remains a valued customer, and we'll continue exploring ways to best meet their needs in the future."
Boeing "competed with a strong but disciplined offer in the Delta campaign," Doug Alder said. "While Delta has chosen to go with Airbus and Bombardier in recent single aisle campaigns, we are proud of the 737 MAX family's superior value and performance."
The decision on the Airbus planes, which was reported Wednesday, comes as Delta is in the middle of a snowballing trade dispute between Boeing and Canadian plane maker Bombardier, which Boeing alleges sold planes to Delta below the cost of production and received unfair government subsidies.
The U.S. Commerce Department recommended a 300 percent duty on those Bombardier jets earlier this year. Delta has repeatedly said it does not plan to pay those proposed tariffs. In a surprise move, Airbus, Boeing's archrival, swooped in to take a majority stake in the contested Bombardier C-Series jet program in October.