The UAA was established last year when United Pictures (UP), a film distributor, merged with The Firm, a law firm.
UAA boasts global networks, heightening the possibility the model-turned-actor will venture into the international movie industry.
The agency has partnerships with China's ATN, founded in Beijing by famous movie producer Terence Chang, and Effigies, a Paris-based artist representation and image consulting agency.
Gang recently finished filming short-movie director Kim Ji-woon's "Hide & Seek" after the actor completed his mandatory military service.