Salmon provides services such as ecommerce, digital consulting, design, delivery and support services to retail, wholesale and manufacturing brands. Other clients include Game, Halfords and Selfridges.
The agency employs 420 people across offices in the UK, China and in Australia, and it will continue to operate as a stand-alone brand and agency within WPP, led by chief executive Neil Stewart.
Salmon was owned by a private parent company, Okam Limited, having been co-founded by its current chairman Chris Harvey in 1989.
In a statement, WPP said the deal reflected the increasing importance of ecommerce to retailers, manufacturers and brand owners, but declined to comment on the financial terms involved.
Salmon’s consolidated unaudited revenues for the year to 31 October 2012 were £34.3m, while its gross assets at the same date were £11.3m.
Sir Martin Sorrell, chief executive of WPP, said "Close collaboration between Salmon and WPP's other agencies will allow WPP to bring clients a tightly-integrated solution across both marketing and technology, and help both the CMO and CIO deliver customer-centric, multichannel solutions – yet another example of where CMO and CIO have to work together."
Stewart added: "With increased client exposure and access to new geographies, our partnership with WPP will help fuel the next stage of our evolution into a global full-service digital delivery agency."