The Nike Plus account was handed to the Miami-based agency earlier this week, following a review that began in early March.
According to an e-mail from Nike, the London office of W&K will continue to create work on the account in the UK, including advertising to promote the "Run London" event - Nike's ten-kilometre run through the capital.
W&K will continue to handle advertising for the sportswear manufacturer's major sporting lines, including football, golf and basketball across the globe.
Just days before the review, Michael Folino, W&K's lead US creative, announced that he was leaving the agency.
It has held the Nike account for 25 years, and was responsible for creating the famous "Just do it" tagline.
During this period, the company's revenues have increased from $3.5 million to $15 billion. Nike now plans to increase that figure to around $23 billion by 2011.