The midfielder was a mainstay of the South Korean team when they took the world by surprise under Guus Hiddink at the 2002 World Cup, which the country co-hosted with Japan.
Yoo scored against Poland to kick off the group stage with a victory, the team going on to defeat Italy and Spain.
He made FIFA’s All-Star team of the tournament that year.
The KFA confirmed his passing with a message: “We will forever remember the shouts and glory of that day with you. Rest in peace.”
Yoo spent his 16-year club career in Asia, playing in Japan’s J-League and his country’s K-League.
He went into coaching, most recently at Incheon United in 2019, but was diagnosed with stage 4 pancreatic cancer that year, forcing him off the bench just months later.
Fans were shocked by the news of his passing and posted messages of condolence online.
“Thank you for gifting us with a great memory, which we will cherish forever,” read one message.
Another fan commented: “A hero to us all, please rest in peace now.”