The bank, which owns the Yorkshire and Clydesdale banks, reported profits of A$1.4bn (£0.94bn) in the three-month period.
That represents flat performance compared with the previous six months, but is below the A$1.5bn analysts expected.
Revenues fell one per cent, largely as a result of higher funding costs in the UK, though business remained strong in Australia.
Meanwhile charges for bad debts fell seven per cent to A$524m – although charges “remain elevated” in Britain, where “asset quality measures continued to deteriorate in the commercial real estate portfolio, reflecting ongoing weakness in the UK economy”.
UK chief executive David Thorburn is stepping down from NAB’s executive committee to focus on the restructuring of banking operations in the country.
The shakeup includes 1,400 job cuts over the next three years as the Yorkshire and Clydesdale move out of commercial property to focus on retail and SME banking.