He joins the agency this week as associate director, from his role as associate director at rival healthcare PR shop Axon Communications.
Zarko-Flynn will be responsible for leading the agency's accounts for AstraZeneca and Janssen, and will take on key responsibilities to assist in running the practice.
His appointment coincides with new additions in Edelman's bioscience division.
Zoey Jackson has been brought on board as associate director after moving from the same role at Ogilvy Healthworld.
Jenny Barrett has also joined as an account manager from Axon, where she was a senior account executive, while Tamena Bashir joins as a junior medical writer.
Zarko-Flynn has more than 15 years' experience in journalism and healthcare communications.
He began his career as a news and current affairs producer with the BBC. During his five years with the broadcaster, he was responsible for daily news and current affairs programming.
He then spent seven years as head of media at Cancer Research UK, before joining Axon in 2008. At Cancer Research UK, Zarko-Flynn promoted the charity's £315m annual research portfolio and developed strategic health awareness campaigns. He also oversaw the charity's award-winning public health campaign to ban smoking in public places and SunSmart, the UK's national skin cancer prevention campaign, funded by the Department of Health.