The WPP-owned company has bought Tagora.com, which specialises in building brand loyalty and adoption, and has reported 2006 revenue growth for 2006 of €3.6m (£2.7m).
Tagora, which is based in Brussels, has a client list that includes Radisson, Carlsberg and Cisco, and has been acquired to boost JWT's global digital marketing reach in fast-growing sectors.
The agency also handles account work for a number of Belgian-based companies, including Nuon, Belgian National Bank and Walibi.
In November, WPP Digital acquired a 75% controlling stake in India's digital marketing agency Quasar Media for an undisclosed sum.
Last year, WPP bought five Chinese agencies, including marketing services company MeThinks in October.