Crumpton, who will start at Mother later this year, will work across a number of as-yet-undecided clients.
She joined McCann London in 2006 and was promoted to McCann Worldgroup’s co-regional strategy director for EMEA, alongside Gary Bonilla, in May 2013. Crumpton has also worked at Fallon as its planning chief.
The appointment follows the departure of Mother’s chief strategy officer, Dylan Williams, who moved to Publicis Worldwide in January. Chris Gallery and Katie Mackay were promoted after Williams’ exit to run the strategy department.
Robert Saville, the founder and creative partner at Mother, said: "Nikki is one of the best strategy brains of her generation and she combines this with incredible warmth and passion."
Crumpton added: "Mother is the agency that has aroused the most professional jealousy in me throughout my career, so to finally get to work there and be part of the magic is an amazing opportunity too irresistible to turn down."