McCann will steer an integrated campaign for the anniversary celebration, including in-store and outside events and the building of a huge 20-metre-high pyramid along Bangkok's busy Rama IV road, opposite Carrefour rival Tesco Lotus's flagship store.
McCann-Erickson out-pitched the likes of J. Walter Thompson, Lowe and the retailing giant's long-time Thai agency, Publicis, to take the two-month contract.
The agency described the battle to secure the short-term project for the world's second-largest retailing group as fierce.
McCann would not reveal how much the deal is worth, but said the Carrefour account was worth an estimated 120 million baht (US$2.7 million) annually.
The carrot for the winning agency is the chance to push a claim to be Carrefour's Thai AOR when the retailer's contract with Publicis finishes at the end of this year.
McCann said its focus was on the project it has won, but it will clearly be hoping for a run at the main piece of business. Carrefour has yet to release a pitch list for its account.