The agency triumphed in a contest against StrawberryFrog Amsterdam, Kirschenbaum Bond & Partners New York, Lowe and the incumbent, Euro RSCG London.
McCann's brief is to create a global umbrella campaign to promote Credit Suisse as a unified brand.
It follows the company's decision to merge its main operation, which offers private banking and financial services, with its investment banking arm, Credit Suisse First Boston, earlier this year.
This resulted in First Boston being dropped after 27 years and an overhaul of its identity and logo by WPP's Enterprise.
The new campaign will break in January, replacing the "360-degree finance" strategy launched by Euro RSCG in September 2001.
Credit Suisse announced its decision to integrate its offering in December.