The year he turned 17, he turned professional and won his debut by KO in the third round. In 1982, he challenged the WBC light flyweight champion Zapata for the first time and lost on decision.
The breakthrough yearThe year he turned 20, he fought Zapata again, won by KO in the third round and became WBC light flyweight world champion. Hankyoreh writes that this fight made Chang known to the world.
In 1984, he beat Katsuo Tokashiki by KO in the ninth round in Pohang for his fourth defense. In 1985, he fought Torres again in his sixth defense.
In 1986, he beat Hideyuki Ohashi by TKO in the fifth round. In 1987, he made his 12th defense at Seonin Gymnasium in Incheon. In 1988, he beat Ohashi again in Tokyo for his 15th defense, then gave up the title.
In 1989, he returned to the ring and challenged González but lost on decision. In 1990, he lost to Chitalada in a flyweight title fight. In 1991, he left the ring after losing to Kittikasem by referee stoppage in the 12th round.
In 2000, he was included in the WBC’s 25 greatest boxers of the 20th century. In 2002, he became head trainer for the boxer Choi Yo-sam. In 2005, he attended the opening of a boxing gym in Busan and coached Choi Hyun-mi.
In 2007, he was a nominee for the World Boxing Hall of Fame but was not elected. In 2009, he was chosen for the International Boxing Hall of Fame. Busan Ilbo wrote that he was the first Korean boxer so honored. In 2010, a celebration of his induction was held at the Korea Boxing Commission.
In 2021, Jjanggu Shelter, named after his nickname, opened in his hometown, Amidong, Busan. In 2023, a film inspired by him, Naneun Paiteoda (I Am a Fighter), was announced. In 2024, he looked back on his fights through the 15th defense in an Asia Today interview. In 2025, he visited amateur boxing tournaments in Anseong and Sejong.
Chang Jung-koo (born Feb 4, 1963) turned professional on Nov 17, 1980, the year he turned 17, and became known when he won the WBC light flyweight world title on Mar 26, 1983, the year he turned 20. He finished his 15th defense on Jun 27, 1988, the year he turned 25.
Ages are by calendar year (the year minus the birth year), birthdays aside.