The move comes as Onken looks to relaunch its brand in the UK.
Onken, which did not previously have a retained agency, used the AAR to co-ordinate a process that originally had Euro RSCG London and Hooper Galton on the shortlist. However, a new set of agencies was invited to compete when Onken rejected the shortlisted shops.
Karmarama's first task will be to develop a new positioning for the brand in an increasingly competitive market via a print, TV, digital and social media campaign.
Laura Graham, the marketing manager at Emmi, which owns the Onken brand, said: "We are thrilled to be working with the team at Karmarama to help us push the brand to a new level and help meet our ambitious plans."
Dave Buonaguidi, the chief creative director at Karmarama, said: "We are really excited. Onken is a great brand for the agency – it operates in a very competitive market, but is very ambitious and great fun."
The Onken brand was purchased by Emmi UK from Dr Oetker last year.