Lankester, a former CEO of Weber Shandwick Asia, will relocate from London to Hong Kong with Edelman.
The agency inherits Limehouse clients including Shell, Canon Europe and DaimlerChrysler.
'My original stomping ground is in Asia, and now I will be strengthening Edelman's regional offering there,' said Lankester, who takes up the post on 18 July. He quit WS to start Limehouse four years ago following a divisional shake-up.
Lankester is expected to help Edelman's existing clients expand into Asia and to support the increasing number of Asian clients looking to build a presence in Europe.
He will report jointly to Edelman Asia-Pacific president Alan VanderMolen and executive V-P of Asia-Pacific and chairman of Hong Kong, Martin Spurrier.
Lankester first joined WS in 1993 and headed its operation in Asia from 1997 to 2000, before taking the agency's UK financial CEO post until 2001.