The forerunners of BankSA were the Savings Bank of South Australia, founded in 1848, and the State Bank of South Australia. These were merged under the name State Bank of South Australia in 1984.

The State Bank of South Australia was sold to Advance Bank due to a collapse and bailout by the Government of South Australia in 1992, when non-performing assets exceeded 30% of the loan book. Advance Bank was purchased by St. George in 1997.

BankSA is now a division of Westpac Banking Corporation, having been a division of St. George Bank before Westpac and St. George merged in 2008.

BankSA has over 100 branches in South Australia and the Northern Territory.