Inferno, which works with Unilever on its Hellmann's, Stork and Bertolli brands, won the business after a competitive pitch.
The agency will be responsible for Dove Spa's first-ever campaign, due to launch in the spring, to raise awareness of its 23 spas nationwide. The work will run across press, DM, digital and in-store, and will be supported by social media.
Inferno will also develop the professional Dove Spa product range, available in-store or through Dove Spa's e-commerce site, and will be involved in plans to refurbish and design the spas.
Dove Spa was launched to capitalise on the mass-market appeal generated by Dove's Campaign for Real Beauty.
Amanda Campbell, Dove Spa's head of marketing, said: "Inferno demonstrated how the Dove Spa brand can create its own identity, while still leveraging all the best bits of the master Dove brand."