Garuda ordered 46 of Boeing's new 737 MAX 8 jets and is converting existing orders for four 737-800s to 737 MAX 8s, the plane manufacturer said.
The purchase is worth $4.9 billion at current list prices, although airlines typically receive large discounts for big orders.
"This order helps continue our commitment to offer the people of Indonesia and Southeast Asia the most comfortable, most efficient air travel in the region," said Emirsyah Satar, Garuda chief executive officer.
The aviation sector in Indonesia, the world's fourth most populous country with 250 million people, has grown rapidly in recent years as an economic boom creates a new class of consumers.
Garuda, a state-owned, full-service airline, is facing stiff competition from budget carriers in the region, such as fellow Indonesian outfit Lion Air - which has expanded rapidly -and Malaysia's Air Asia.