He succeeds long-standing MD Cherry Wood who resigned after 11 years to launch her own agency (PRWeek, 05 September 2008).
Carroll has been acting as a freelance senior consultant since his departure from heading up Fleishman Hillard's pan-European healthcare practice in 2005.
Previously, Carroll also worked as a GP and a freelance medical journalist and writer.
Carroll will head up a senior management team at Athena that includes consultant Tessa Hopkins and business unit directors Jennifer Wilson and Sharon Poole.
Wood is set to leave the agency in October to set up her own ethical medical and healthcare public affairs agency. She was hired in October 1997 to launch Athena.