The move means the car-maker has cut ties with Singleton Ogilvy & Mather and Ideaworks, which both worked on Hyundai, and Brave, which handled Kia.
Innocean already works on the Hyundai business in several other markets around the world, including in India and Germany.
It broke into the Australian market towards the end of 2008, when Hyundai charged the agency with overseeing the consolidation of its media duties, which were won by Initiative.