Burns, 42, who has been working on a consultancy basis in the US for the past two years, joins on February 27.
Her task is to turn around the London shop, which lost £60m in billings last year, and hire a new planning director to replace Russ Lidstone, who quit to join Euro RSCG London last week.
She will work closely with Toby Hoare and Nick Bell, the agency's executive chairman and executive creative director respectively. However, there are no plans to replace Mark Cadman, JWT's managing director, who left with Lidstone.
Burns, who is British, said: "JWT's client list is mouth-watering and fits my experience and passion for big brands that matter to a broad consumer church."
She started her career in the UK in 1984 as a trainee account handler for Fletcher Shelton Delaney. After holding several agency positions in this country, including a stint at Young & Rubicam, where she worked with Hoare, she moved to the US where she became PepsiCo's vice-president of marketing. Then she spent five years as Fallon New York's president.
Bolton left JWT following a difficult year in which the agency lost business including Samsung, Persil and Axa. He is now the chief executive of WPP's Enterprise IG.
Hoare has been caretaking the chief executive role over the past two months. He said:
"Alison brings to JWT a broad international perspective. She shares my passion for team-building and her experience stands her in good stead."
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