The win sees Karmarama join Unilever's roster. The brand has not advertised since the late 90s.
Beil Gledhill, Coleman's marketing manager, said: "We liked Karmarama's willingness and ability to work across a variety of channels, including everything from advertising to licensing ideas."
The win comes in the same week that the agency was appointed to launch Zopa, an online financial brand.
Zopa aims to allow individuals to borrow money from other individuals, with the lender setting the risk, terms and interest rates of the loan.
Advertising is planned for later this year. Zopa's team is headed by the former Egg executive Richard Duvall.
Duvall said: "Zopa understands that people are starting to reject one-size-fits-all products or services because they are realising that their own size is much better. Karmarama has a similar approach to communication."
Zopa was launched in March via a public relations campaign through Sputnik Communications.