Yun was trained in the Power Plant, the World Championship Wrestling farm territory. He worked in WCW until its closure in 2001. During the following years, he worked for several promotions. In United States, he worked with Total Nonstop Action Wrestling (where he was part of the promotion's first match) or Ring of Honor, but most notably with World Wrestling Entertainment, where he had three different stints from 2001 to 2002, 2003 to 2005 and 2006 to 2010. During his last stint, he wrestled as Jimmy Wang Yang, a Japanese-American cowboy.