"The A321neos will inject growth possibilities to our network plans for 2020 and beyond," Scoot CEO Lee Lik Hsin said in a statement.
The jets will be fitted with 236 seats, 50 more than on its A320neos, the airline said. Deliveries are due to begin in the last quarter of 2020, with the planes to fly routes within six hours of its Singapore base.
"We are pleased that Scoot is adding the A321neo to its fleet," an Airbus spokesman said in a statement.
Scoot, which has 37 A320neo family jets on order, had once planned to take 14 Boeing Co 737-800s from Singapore Airlines regional arm SilkAir.
Those plans were shelved after the global grounding of the 737 MAX jet because SilkAir required the aircraft to replace lost 737 MAX capacity.
(Reporting by Jamie Freed; Editing by Muralikumar Anantharaman)