Consilium said Gardner, who takes up his post on Monday, will help establish it as "the leading international healthcare communications agency and lead client accounts".
Gardner has more than 15 years of experience in strategic comms in the healthcare sector and was a director in the life sciences team at Citigate Dewe Rogerson between 2003 and 2015.
Previously, he was an associate director at the bioscience comms consultancy HCC De Facto.
Mary-Jane Elliott, managing partner of Consilium, said: "We are pleased to welcome Chris to the growing team at Consilium and are excited to bring someone of his seniority and depth of strategic healthcare communication experience to complement our world-leading healthcare communications offering."
During Gardner’s career, he has led comms strategies on cross-border IPOs, private fundraisings and international merger and acquisitions and he has experience in profile-raising campaigns and crisis comms.
Gardner said: "[Consilium] has an exceptional client base and I look forward joining the team and working with it as the business continues to develop and deliver outstanding communications consultancy."