BSP traces its history to 1 May 1957, when the National Bank of Australasia established a branch in Port Moresby.

BSP conducted public offerings in 1980 and 1981, with the result that local citizens came to hold 13% of the bank's shares.

In 1993, National Investment Holdings Limited (NIHL) first acquired NAB's 87% shareholding, and then the 13% of the shares in the hands of the public, giving it 100% ownership of BSP.

In 1995 the government decided to increase the bank's capital base, which it achieved by selling a 25% stake to Credit Corporation (PNG) and a 22% stake to Motor Vehicles Insurance (PNG) Trust (now incorporated as Motor Vehicles Insurance Limited).

In April 2013, BSP sold the Niue branch to New Zealand bank Kiwibank.

BSP also acquired Habib Bank (Fiji), which had begun in 1991 as a branch of HBL Pakistan.

WBC offered Samoan investors, who held the remaining shares, the same price it had paid Bank of Hawaii.