The agency began working on the business in 2008 when it broke away from micro-network StrawberryFrog, taking clients including Panasonic, Chevrolet, Opel, Asics and Onitsuka Tiger.
Following the split, Asics Europe consolidated its regional creative business into Amsterdam Worldwide. StrawberryFrog had worked on the brands since 2001.
The Asics portfolio includes Asics performance wear, Asics SportStyle, Ayami and Onitsuka Tiger.
Brian Elliott, founder and chief executive of Amsterdam Worldwide, said: "Our team has built one of the most iconic sports fashion brands in the world over the past decade – and done so on the most modest of budgets.
"The decision to resign a piece of business is not an easy one, but strategic, creative, and financial differences with Asics mean we can no longer continue our relationship.
"We wish them well. We will always have great passion and love for the brands, and are proud of our accomplishments together. We have taken both Onitsuka Tiger and Asics a long way, and it's time to move on."
Last year the agency won a Gold Design Lion at the 2010 Cannes Lions Festival for its brand campaign for Onitsuka.
In December Asics launched a pan-European digital campaign to find the face for its Ayami women's sportswear range.