Smith is being promoted from 1 September to head up the agency's corporate practive, EMEA.
He will also join H&K's European executive committee.
He will be responsible for developing the company's corporate practice across the region and its growing roster of international corporate clients.
He will be based in London and report to EMEA chairman and CEO Andrew Laurence.
Smith resurfaced at H&K in October last year after being squeezed out as former Edelman UK CEO in April.
Smith's head of UK corporate role will be filled by Tarquin Henderson who joins in September.
He was most recently COO of the corporate and brand team at City agency FD.