Thorburn said he expected the business and private banking units would be most affected but that no targets had been set.
Releasing its full year results, NAB said a reshaping of its workforce would see the creation of 2000 new jobs to 2020, though overall about 6000 roles will be impacted as the bank accelerates its strategy to grow and maintain productivity.
One-off restructuring costs related to the redundancies of between A$500 million and A$800 million are expected to appear in the bank's first-half results next year. The shares are up just over 7% for the year so far.
There will be a loss of 6,000 jobs over three years but the bank's chief executive, Andrew Thorburn, said the net loss would be closer to 4,000 as 2,000 new digitally focused positions will be created.
Thorburn highlighted the bank will happily retrain those who have the aptitude and commitment to do so, though he said that numerous job cuts will be in more "traditional" areas of the bank.More news: White House opposed vote on Israel 'annexation' bill
The result was in line with analyst expectations and NAB held its final dividend flat at 99 cents, fully franked.
The bank's outlook remained positive as it forecast an upturn in business investment and government spending.
NAB shares ended 2.83 percent lower at AU$31.95. "And I think it's important we face into that and we have a clear plan and we talk with our people about it".
Interest rate levels have become a hot-button political and customer issue in Australia this year, with the corporate regulator pledging to investigate whether banks are using a push to curb a potential housing bubble as an excuse to profiteer through unnecessary mortgage rate rises.
The overhaul comes with the bank's net profit bouncing back in the year to September 30 from only A$352 million in the same period last year, when it took a hit from writedowns for loss-making assets.