Feenan will be responsible for divisional development and project delivery at the Cambridgeshire-based events agency.
She was most recently a freelance consultant, before which she held posts at companies including Threesixtythree in Canada and Karen Earl Sponsorship. She has managed events for brands including Jaguar Land Rover, Barclays and Ernst & Young.
Stephen Casey, Accio's managing director, said: "We already have an impressive client list that spans corporate and consumer brands, not to mention the Royal Household, but we cannot afford to be complacent.
"I am looking to grow our corporate events business over the coming years and Clare brings world-class pedigree to our proposition."
Feenan added: "Since returning to the UK and taking a brief maternity break, I've been keeping up to speed with the event world and I was thrilled to get the offer to join Accio at this exciting stage in its development.
"I'm looking forward to leading the Accio Events team, and delivering projects with the same creativity, professionalism and outstanding attention to detail that has become the trade mark of the Accio Group."