
Longley, who joins JWT at the end of October, will lead the Special K account as well as working on other yet-to-confirmed projects.
She will report to JWT's executive creative director, Russell Ramsey, and work closely with Paul Banham, the agency's recently appointed digital creative director.
Ramsey said: "While Nicholla has worked on some fabulous campaigns at Wieden & Kennedy, it is her breadth of experience in the design field and outside traditional communications that made her really stand out."
AT W&K, Longley has worked on campaigns for Nike, Honda, Lurpak, Cravendale, The Guardian and Nokia.