Razorfish, which pitched against undisclosed agencies, will assist with strategy and the launch of new markets and products for both brands.
The agency already handles Unilever brands Axe, Lipton, Rexona and Signal.
In March, Unilever chief marketing officer Keith Weed said the company was looking to reduce the number of digital agencies it worked with.
At this year’s Cannes Lions festival, Unilever chief executive Paul Polman praised the "influence of media companies such as Facebook, Twitter, MSN, Microsoft, Google and Apple".
Last month, Unilever launched its ‘Body Language’ campaign for the new Dove hand and body range, to promote the new range across Europe.