Dennis will return to the position he held between 1982 and 2012 and also retains his role as chairman of McLaren Group.
Dennis was McLaren's team principal in Formula 1 between 1982 and 2009.
"My fellow shareholders have mandated me to write an exciting new chapter in the story of McLaren, beginning by improving our on-track and off-track performance," he said.
"Over the coming weeks I intend to undertake a thorough and objective review of each of our businesses with the intention of optimising every aspect of our existing operations, whilst identifying new areas of growth that capitalise on our technologies, and where appropriate further investing in them."
"During February, I will articulate a new Group strategy and implement the organisational structure best suited to achieving it. I am excited by the prospect of returning to the role of Group Chief Executive Officer and working with my many colleagues and fellow shareholders to fulfil our objective – which is to win at whatever we do."
McLaren finished in fifth place in the 2013 Formula 1 world championship.
McLaren did not say where this left Whitmarsh, who has been team principal since 2009.