Four executives from the Seattle-based agency have relocated from the US to set up in Wunderman's London office.
The fledgling outfit, which specialises in large-scale user testing of websites to boost conversion and user experience, has already won work from Wunderman London clients Nokia and Ford.
"We've spent the last 10 years helping clients build complex web presences," said Brendan Tansey, Wunderman London's CEO. "Very little of that investment has gone into a robust understanding of consumers' website journeys and the things that make money for brands on their sites. With that understanding, brands can ensure they don't lose a single conversion."
Tansey said the hope was that Zaaz grows to become a 20 to 30-person outfit in London.
WPP-owned Wunderman acquired Zaaz, whose clients include Dell and Expedia, in 2006 and in January took a 3.5% stake in web analytics firm Omniture.
WPP plans to shift its own technology and data products onto Omniture's platform over the next year. This includes 24/7's ad-serving systems and the data collection platforms of WPP's recent market research acquisition, TNS.