Phelan, a senior public affairs and international communications executive based in London, has been promoted to executive vice-president and MD international corporate comms.
He will lead the London-based team working with clients across MENA, Africa and the firm's global network.
Greg Prager, a senior client leader in the company’s Geneva international consulting team, has been made chair of Weber Shandwick’s EMEA corporate practice.
The firm said Prager would be "leading the development of best practice, talent, new business and innovative corporate brand solutions for clients", working in partnership with US-based global corporate practice chair Micho Spring.
Phelan and Prager will both report to UK & EMEA CEO Colin Byrne, who said: "This timely restructure seizes an opportunity to see corporate practice development, and our growing international and emerging market corporate comms business, acquire senior leaders in their own right.
"This reflects the growth and importance of both areas to our clients and our firm."
Jim Donaldson, who led Weber Shandwick's international work out of the Middle East and chaired the firm's EMEA corporate practice for the past three years, will leave the firm at the end of December. He will join FleishmanHillard in January a new role heading the group's UK and Middle East operations.