The order had previously been accounted for on Chicago-based Boeing's Orders and Deliveries website, but had been attributed to an unidentified customer.
Garuda will buy 46 of the fuel-efficient, single-aisle 737 MAX 8s and convert existing orders for four Next-Generation 737-800s to 737 MAX 8s.
Garuda said it currently operates 77 Boeing 737s and that the new order would give it the flexibility to grow and update its fleet as the market demands.
Garuda said in November of last year that it planned to add up to 250 aircraft by 2025 to effectively double its fleet and meet demand in one of the world's fastest-growing aviation markets.
Reporting by John McCrank in New York; editing by Matthew Lewis