The WEF, which organises the annual meeting of global business and political elites in Davos, said Brown had "valuable insights into the global agenda" from his ten years as British finance minister and three years as premier.
Brown will chair a new "policy and initiatives coordination board," an informal group of heads of international organisations and government representatives, the WEF said in a statement.
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"With the challenges the world faces, it is vital that all stakeholders are engaged in solving them. The World Economic Forum is uniquely placed to bring those stakeholders together and support the global agenda," Brown said.
The 60-year-old had been tipped as a possible leader of the International Monetary Fund but the suggestion was dismissed last week by current British Prime Minister David Cameron, who ousted Brown in elections in May 2010.
Cameron said the former premier may not be an "appropriate" candidate, noting that by the time he left office, Britain had racked up huge amounts of debt.
Announcing Brown's new role, the WEF highlighted his "key role" in coordinating the international response to the financial crisis, including by hosting the Group of 20 summit in London in April 2009.
It also noted his contribution to the Group of 8 agreement struck in Scotland in 2005 to support poor countries, to renegotiate their debts and to tackle climate change. At home, he also oversaw the world's first climate change act.
"Gordon Brown will bring a wealth of knowledge and experience to the World Economic Forum," said Klaus Schwab, the WEF's founder and executive chairman.
He said Brown "has valuable insights into the global agenda that will complement and inform many of the forum's initiatives."
The forum said Brown would not be paid for his role but it would provide him with support staff.
