Smart Media said it came ahead of Britain's Addison which was part of WPP, the world's largest advertising group.
"We have been ranked among the top five agencies in the world for three consecutive years," Vijith Kannangara, chairman of Smart Media said in a statement.
"What is significant in our Asia Pacific regional Platinum is that no other agency from South Asia has been placed.
"The Gold, Silver and Bronze of the region have been awarded to two of Hong Kong's giants and a South Korean giant respectively."Smart Media said it had won the awards for a the second year running.