The business will now operate under the FD Third Person brand, working alongside FD's existing Sydney and Melbourne offices.
The Perth consultancy is owned and managed by directors Paul Downie and John McGlue.
'The change to FD will provide our clients with access to the best of what the group does nationally and internationally, plus the benefit of exceptional on-the-ground services in major business and investor centres around the world,' said McGlue. 'FD is by far the best fit for our clients and our business.'
Downie established the Perth office of Porter Novelli in 1993, having previously managed an agency specialising in the mining and finance industries.
McGlue acquired a 50 per cent interest in Porter Novelli Perth in 2002.
FD has now opened five new offices in 2008, taking its global presence up to 27 cities worldwide.