In the newly created role, Walton will be charged with developing an "innovative and ambitious" brand strategy for the children's charity.
She will manage a new brand team and work across all of Unicef’s fundraising and advocacy departments, in an effort to "maximise the organisation's voice", according to the charity.
Walton, who spent seven years at Save the Children, has also worked for brand consultancy Wolff Olins, where she provided brand strategy advice to clients, including Amnesty International, Macmillan Cancer Support and Unilever.
Jane Cooper, director of communications and brand at Unicef, said Walton brought "an impressive breadth of skills and expertise" to the "important new role".
Established in 1956, Unicef UK is one of 36 Unicef national charitable organisations based in industrialised countries that work to raise money for the charity's global work for children, as well as working for the rights of children in the UK.