The Bahraini national carrier will lease two Airbus A319-100 aircraft and three Airbus A330-200s for six years from the US group.
The short-haul A319-100s are scheduled for delivery before the end of August, while the medium-to-long-range A330-200s will arrive between March and May next year.
The airline currently has a fleet of 27 aicraft after downsizing early last year as part of a restructuring of the company. However, under Bjorn Naf, the new chief executive officer at Gulf Air, the company has sought to expand. Earlier this year the company placed firm orders for 61 new aircraft.