The business was previously handled by CHI & Partners but the agency parted ways with the company in January just nine months after winning the account.
Yellow Door, which was founded by the retail expert and TV celebrity Mary Portas, won the account after a pitch against Leo Burnett.
The agency will handle all advertising for Westfield West London and for its Stratford City development, which has a catchment area of 4.1 million people and will house John Lewis, Waitrose and Marks & Spencer. Straford City is due to open in September.
Before appointing CHI in April last year, Westfield used Adam & Eve on its advertising business. The agency handled creative for two years but was forced to resign it after it won the £20 million John Lewis account.