The source said an official announcement was imminent from Italy, where prime minister designate Matteo Renzi is soon to unveil his new cabinet.
Padoan has been deputy secretary general of the OECD since June 2007 and chief economist since December 2009, according to the organisation's website.
He served as economic advisor to two Italian prime ministers from 1998 to 2001 and then became Italian executive director at the International Monetary Fund until 2005.
He has also been a consultant to the World Bank, European Commission and European Central Bank and is the author and editor of several books as well being widely published in international academic journals.
ANSA news agency reported on Friday that Padoan is returning to Rome from the Group of 20 nations meeting in Sydney to accept the position.