O’Kennedy, who leaves after two years in the position, has stepped down to support his children as his wife pursues a private business venture.
Lindsay is a former chairman of Publicis UK and former president of TBWA UK and Ireland.
The appointment was ratified by a unanimous vote of the D&AD executive, but has been kept under wraps until this morning.
Lindsay will take charge in the run-up to the charity’s 50th anniversary in 2012 and the launch of its new White Pencil award, which aims to reward creative work merited with changing the world for the better.
O’Kennedy has been credited with seeing a rise in submissions and membership to the organisation, which provides professional development to the creative industries.
Both men will work together in a transitionary period before a formal handover takes place at the annual D&AD Presidents’ Dinner on 21 September.
Lindsay’s other roles include non-executive director of Media Square and advisor to two start-up businesses. D&AD confirms that he will continue in all of these roles.