Ostrowski, who took the helm in 2008, will take a seat on Bertelsmann’s supervisory board, the German company said, adding that he was making the switch for personal reasons.
The move comes as a surprise as Ostrowski’s term runs until December 2012, although Bertelsmann has traditionally decided to extend contracts for top jobs a year before they end.
Finance chief Thomas Rabe will take over as chief executive at the start of next year. It was an open secret that Rabe had been vying for the CEO position, but whenever he was in talks to leave had been persuaded to stick it out at Bertelsmann.
Rabe and Ostrowski were known to be at odds partly due to their different styles and personalities, but company sources have said the two had put their differences to rest.
Ostrowski had spent his whole career bar two years working for Bertelsmann at the group’s headquarters in the small town of Guetersloh, less than 20km where he was born.