Di Leo will join in early September as head of public affairs in the UK, leading a 12-strong team.
In addition, Stephanie Bailey, who joined FleishmanHillard in April as a director and partner, has been given the new role of head of corporate, reporting to a newly formed reputation management group led by Sophie Scott.
The shake-up follows the departure earlier this year of Nick Williams, FleishmanHillard’s UK head of public affairs and corporate comms. It also comes as amid rumours that FleishmanHillard is to merge with fellow Omnicom agency Fishburn with news that the two are to share offices from the autumn.
Di Leo, who has more than 20 years' experience in public affairs and strategic comms, will report to Jim Donaldson, MD of the UK and Middle East, who said: "Michelle’s addition to our senior leadership team underlines our commitment to build on FleishmanHillard’s strengths and expertise in public affairs, one of our core offers in the UK.
"I am confident we will go from strength to strength under her leadership."
Di Leo said: "I'm looking forward to playing my part in a team that is creative, effective and focused on delivery for clients."
Before joining Teneo, di Leo worked at Heathcroft Communications. She also had PR and public affairs roles at the National Union of Teachers, the British Lung Foundation and the Airport Operators Association, and worked at agencies LLM Communications and FD Public Affairs.