Harris replaces Steve Harrison, the worldwide creative director and co-founder of Harrison Troughton Wunderman, who departed in May to pursue other interests.
Harris is the first senior appointment made at Wunderman since WPP decided to axe the HTW name and roll the agency into Wunderman Automotive in July.
At the time, Trish Wheaton, the president of Wunderman in Canada, was drafted in for an interim period in order to oversee any senior hirings at the agency. Harrison's departure was followed by that of the agency's chief executive, John Butler, who left when the agencies merged.
The agency has yet to appoint a new chief executive, so, in the interim, Harris will report directly to Wheaton.
Wheaton said: "Dave is delightfully collaborative, and he is digital-savvy, which is where Wunderman is focusing its investment."
Harris said: "It is great to be joining Wunderman at this exciting stage of the company's development. This opportunity combines the best of both worlds for me. It has the entrepreneurial feel of a start-up (albeit a particularly large one) combined with the backing from a global network."
Harris left Lida in March amid rumours that he was plotting a start-up.
Before setting up Lida with Lisa Thomas in 1999, Harris filled the position of executive creative director at IMP for four years.
His career also includes a stint as a senior art director at McCann Erickson.