He was appointed to the DBCM board in August 2002, it said in a statement.
Petersen succeeds David Noko who stepped down at the end of March.
In addition to his appointment as CEO of DBCM, Petersen also heads up the South African mining interests of the De Beers Family of Companies.
Gareth Penny, De Beers Group CEO, said Petersen led a company already far more efficient than it was a few years ago, having learnt from the recent experience of the global economic downturn.
"I am confident that Barend will make as significant a contribution to De Beers in his executive role as he has made in his non-executive role in the past decade."