The additions will give the Scandinavian low-cost carrier a total fleet of 80 aircraft by summer 2023.
The lease agreements with AerCap also includes eight Boeing 737-800 NG, which are part of the 70 aircraft fleet operational for the summer 2022 season.
"The addition of these aircraft will help us achieve our target of building a larger, modern and more fuel-efficient fleet," Norwegian chief Geir Karlsen said.
"This will in turn enable us to deliver our products and services in a wide network of routes in the Nordics and to European destinations."
The Boeing 737 Max 8 is approximately 14% more fuel efficient compared to previous-generation aircraft, and will contribute to Norwegian’s target to reduce its carbon emissions by 45% by 2030, compared to 2010.
The carrier has previously announced several lease agreements that will increase its fleet from the current 51 aircraft to this summer’s fleet of 70.
For some of the aircraft under these agreements, Norwegian has the option to substitute certain aircraft with equivalent narrow-body models from Airbus.