Warne is Test cricket's second most successful bowler with 708 wickets in 145 tests, after Sri Lanka's Muttiah Muralitharan's 800.
Warne said he was "blown away" by the generosity and the final figure was "way beyond my expectations".
Warne, 50, is one of many domestic and worldwide athletes, from cricketers and tennis players to Australian NBA players, to have pledged to support the fundraising for bushfire victims.
The online auction ended on Friday morning and Warne's baggy green doubled the record amount paid for one of Don Bradman's caps, which went for 425,000 AUD in 2003, with 100 per cent of proceeds to be donated.
On Friday afternoon, Commonwealth Bank revealed they were the mystery victor of the auction, sharing they intend to exhibit the cap in the Bradman Museum in Bowral after a national tour.
"I am delighted that CBA has been able to secure Shane's cherished baggy green cap", Comyn said.
The Commonwealth Bank of Australia (CBA), which sponsors Cricket Australia, confirmed in a statement on Friday it was the successful bidders and would take the cap on a nationwide tour to raise more money for bushfire relief.
Social media lit up with praise for the Spin King.
Warne was overwhelmed by the frenzied interest in the rare piece of memorabilia, sending a thank you note after the auction closed, via his Instagram page.
"The horrific bushfires in Australia have left us all in disbelief".
The baggy green is presented to Australian players at their Test debut and they receive just one for their entire career.
Warne chose to put the cap up for auction on Monday to help those who have suffered in the catastrophic fires that have devastated parts of the country and left at least 26 people dead and nearly 2,000 homes destroyed.
Writing when he launched the auction, Warne said: "Lives have been lost, homes have been destroyed and over 500 million animals have died too".
Six-times Formula One world champion Lewis Hamilton said on Thursday he was donating $500,000 towards the rescue and care of wildlife caught in the bushfires.
Top tennis players have also got involved, with world number one Ashleigh Barty donating her winnings from this week's Brisbane International to the Red Cross, although she was knocked out at the first hurdle.