Grayling will not be hiring a direct replacement, but the agency said it would unveil a new UK creative director in the near future.
Cohen will join Lewis on 5 June as senior vice president EMEA brand, reporting to Munich-based EMEA executive vice president Andres Wittermann, Executive Vice President.
He has been in his current role since the start of 2016 when Grayling's UK brands arm merged with Atomic. He first joined parent firm Huntsworth with Harrison Cowley, which was later merged into Trimedia, with Cohen becoming UK MD. He has been the EMEA MD of Atomic since 2012.
Cohen is listed in the PRWeek UK Power Book and has experience working for clients including Pernod Ricard, Nestlé, British Airways, Avis, Coca-Cola and Hilton.
While better known as a tech agency, around a fifth of Lewis' global business is in consumer, and more than a quarter in EMEA. Clients in the region include recently won Dutch retailer HEMA and audio equipment firm Jabra.
Wittermann said Lewis had "big plans" for the consumer and digital team, saying: "In this hyper-connected world, we need to fuse the creative with the imperative, and Daniel’s tremendous experience with blue-chip brands will be a fantastic addition to the EMEA leadership team."
Sarah Scholefield, UK and Ireland MD at Grayling, said: "Daniel has played a significant role in the evolution of both agencies, and has established a strong legacy in delivering highly creative, integrated campaigns. This legacy will carry on in both Grayling and Atomic, who will continue to deliver effective, high-profile campaigns that provide measurable advantage to our clients under new creative leadership.
"We have appointed a new creative director for the UK and will be making an announcement regarding this role in the near future."