In a statement, the retailer said it has decided to "take advantage" of its "growing in-house creative and strategic resources to develop its broadcast advertising, but will continue to utilize outside strategic, creative and production resources on an as-needed basis."
The Boston agency, whose parent is Interpublic Group of Cos., emerged the winner after a review last year.
The move doesn't affect Toys "R" Us' media agency, WPP Group's Mediaedge:cia.
The retailer in 2007 spent $98 million on domestic measured media for its Toys "R" Us and Babies "R" Us brands, up slightly from $91 million in 2006, according to TNS Media Intelligence.
The departure of the account isn't expected to affect staffing at the agency, whose other clients include Bank of America and Dunkin' Donuts, a spokesman said.
"We have nothing but respect and admiration for Toys 'R' Us. ... We're proud of our strategic and creative work on their behalf, but are realistic that it's best for each of us to part ways at this point," said Hill Holliday CEO Mike Sheehan in an e-mail.