The review will be run from Remington's New York base. A spokesman for Remington said the review followed a "re-evaluation of global brand and strategy".
The company spent £2.34 million in the UK in the year ending 31 January, according to Nielsen Media Research.
Karen Shepherd, the Remington UK managing director and the former international marketing director, said: "We have had a fantastic partnership with Grey, which ultimately led to the 'it's what's on the outside that counts' campaign, which gave Remington stand-out in a highly competitive market."
The Grey deputy chairman, Nicola Mendelsohn, said: "We wish them well for the future."