Al-Zaidy will take charge of the strategic direction of the agency. Before TBWA, he worked at Rainey Kelly Campbell Roalfe/Y&R.
Crumpton, who joined McCann in 2006 as the planning head, has been promoted to co-regional strategy director of McCann Worldgroup Europe, alongside Gary Bonilla.
Gustavo Martinez, McCann’s president of Europe and Asia-Pacific, said: "Both Nikki and Zaid have the depth and breadth of experience to set the strategic direction across London and Europe."
McCann London’s president, Chris Macdonald, was announced as the president of the New York unit last month.