Kavanagh joins JCDecaux following the departure of Pierre Jeanjean, who stepped down in January after 23 years at the company.
She will join the executive board and oversee the running of its street furniture business across roadside and retail environments.
Prior to her new role, Kavanagh was franchise director for London rail and retail at CBS Outdoor, managing all London rail advertising contracts including the London Underground. She was also responsible for the launch and management of CBS Outdoor's retail presence in the UK.
Kavanagh joined CBS Outdoor in June 2007 as commercial director, London rail, from Titan Outdoor (formerly Maiden Group) where she was development director.
She joined Maiden in 1995 where she was responsible for all roadside and retail development and contract management.
Her earlier career included roles at Mills & Allen (now JCDecaux) and More O'Ferrall (now Clear Channel).
Jeremy Male, chief executive officer of JCDecaux, said: "I am very pleased to welcome Helena to the board of JCDecaux. She has enormous experience of the outdoor sector and her experience will be invaluable as we develop our street furniture business further."