At list price the value of the firm order for the new long-haul jets is about $4 billion, while the total amount would go up to $6 billion if options are firmed up in the future.
The airline announced in November 2007 that it was planning to renew its entire fleet saying it would order up to 35 planes.
Bjorn Naf, Gulf Air's newly appointed chief executive had said that the company was holding intensive talks with Boeing and its European rival Airbus, but he did not rule out leasing some aircraft.
Gulf Air aims to build up a fleet of 45 to 50 aircraft by 2013, Naf said.
The announcement of the Boeing order came as George Bush, the US president started a two-day visit to Bahrain.
It is the first time a US president has visited Bahrain, which is home to US Navy’s Fifth Fleet and one of the few Middle Eastern states to have a free trade deal with the US.
Gulf Air was founded in 1974 and was owned equally by the governments of Bahrain, Qatar, Abu Dhabi and Oman.
Qatar and Abu Dhabi withdrew in 2002 and 2005 respectively, both investing in thier own airlines - Qatar Airways and Etihad. Oman got out in May 2007 to inject more money into Oman Air.
The announcement of the order by the Bahrain airline comes 10 months after it revealed that its projected debt at the end of 2007 would be $676 million.