Holbrook will replace Jonathan Bland, who has been chief executive of the coalition since it was formed six years ago, in early 2010.
Bland will remain as chief executive of the coalition until 31 October, when he will leave to form an international social enterprise consultancy. He will also take up an advisory role with the coalition.
Holbrook said he was honoured to take on the role.
"Politically and economically, social enterprise is set to be tested like never before," he said. "But alongside the undoubted challenges that face the sector, we have a unique opportunity to promote an economic model that can change not only the way we do business but also society at large."