In addition to worldwide branding strategy, Mr. Costello is charged with unifying Yahoo!'s North American marketing initiatives and developing more effective marketing solutions for Yahoo! clients.
Among his charges is supporting Yahoo!'s strategic corporate intiatives, including development and marketing of consumer pay services, the company said in a statement.
Murray Gaylord, vice president of brand management, will report to Mr. Costello, who in turn will report to Greg Coleman, executive vice president of North American operations.
News of Mr. Costello's move to Yahoo! was first reported on Adage.com
Mr. Costello replaces Yahoo!'s long term marketing chief, Karen Edwards, vice president of brand marketing, who left earlier this year.
Havas' Advertising Black Rocket Euro RSCG, San Francisco, is Yahoo's agency and is responsible for Yahoo!'s "Do You Yahoo!" tag line.