Seifert, who is managing director client services at WPP-owned O&M New York, is to replace Carl Johnson who was last year named chief operating officer of TBWA\.
Talks are thought to have been going on for some time to find someone to take over from Johnson, who took up his new role while still running TBWA\Chiat\Day in April 2001.
It is unclear when Seifert will take up her new position. At O&M, she worked on accounts including the agency's £276.8m AT&T Wireless account, which it picked up last year.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .