The agency won the business without a pitch. It will create campaigns to relaunch both theme parks ahead of the introduction of new attractions due next year.
The hiring strengthens DLKW's relationship with the parent company Merlin Entertainment Group, formed after Merlin and the Tussauds Group merged earlier this year. DLKW already handles Legoland, and won the Alton Towers account in September.
Separately, Merlin Entertainment Group has hired Trinity Communications to work on digital and communications planning for Alton Towers. It will work with the media agency Manning Gottlieb OMD on the business.
Andy Raven, a managing partner at DLKW, said: "There's no bigger compliment than additional businesses within a client group choosing to work with the same agency. Both parks have very clear propositions, which we look forward to helping develop next year."