Jeon has won three consecutive world championships (1993, 1995, 1997), twice beating the Hidehiko Yoshida in dramatic fashion in the finals. He has also won six world cup titles.
The crowning moment in Jeon's judo career came in winning the gold medal in the men's middleweight division at the 1996 Olympics in Atlanta, U.S. He defeated Armen Bagdasarov of Uzbekistan in the final match by ippon. In his march to the gold, Jeon won every match by ippon, except the 1st round match against the Dutch judoka Mark Huizinga, who would go on to dominate the weight once Jeon himself retired.
Jeon retired from competition at a relatively young age of 25 in 1999, citing both knee injuries and an absence of motivation due to lack of competition. He retired undefeated in both Olympic and world championship competition.
In 2003, PRIDE FC and Antonio Inoki tried to sign Jeon to fight Yoshida under MMA rules (using the fact that Jeon have never lost against Yoshida in judo) but Jeon refused offers.