Hwang joins from Y&R New York, where he worked on accounts including Diet Dr Pepper, Texaco and Toys R Us. He was previously a creative director at BBDO New York.
Gavin Heron, the TBWA\China group chief executive, said: "Chien stood out among a number of very good candidates. His global experience in New York and his enthusiasm for China and the TBWA brand really appealed."