Spink won the work following a non-competitive pitch.
The agency will build awareness of the brand, develop a TV advert and work on product launches for 2016.
Jo Spink, director of the agency, said: "Kalms is a fantastic addition to the Spink portfolio of wellness brands and we have some exciting plans to bring to life the new TV creative LiveLifeReady."
Meanwhile the agency has appointed James Butcher, the former parliamentary aide to Tim Loughton MP, as a senior account executive. Butcher headed up the campaign to re-elect Loughton and was responsible for all media communications.
In his new role at Spink Butcher will work with clients including BEAMA, the trade body for the energy and power industry; United European Gastroenterology, and Orchid, the UK charity devoted to research and treatment in men's cancers.