The world's biggest miner recently sold its US shale oil and gas operations to British giant BP for US$10.5 billion, and said it would return the funds to shareholders.
The special dividend of US$1.02 a share will be paid out in mid-January. The stock buyback was set at Aus$27.64 per share.
"Completion of this programme will bring total cash returned to shareholders to US$21 billion over the last two years," BHP chief financial officer Peter Beaven said in a statement.
BHP's sale of the US assets was at a heavy loss, after it had bought the operations in 2011 for US$20 billion.
The impairment charges from the sale saw BHP post a 37 percent slump in annual net profit to US$3.7 billion in the year to June 30.
The Anglo-Australian firm has announced or completed more than US$18 billion of divestments over the last six years to focus on its most profitable core long-life operations -- iron ore, copper, petroleum, coal and potash.
Shares in BHP were trading 1.36 percent higher at Aus$32.84 in Sydney on Monday.