Basilio was Dundee's first world champion, after he defeated Tony De Marco for the world welterweight crown. From there on, Dundee began receiving many young talents at his gym, helping polish some of the greatest boxers in history.
Dundee shot into national fame when Ali conquered the world Heavyweight title from Sonny Liston. Even as Ali became a member of a radical, Black muslim group during that era, he refused to let Dundee, a White man, go. Some Black Muslims, such as Elijah Muhammad, allegedly tried to pressure Ali to separate from his trainer, but Ali and Dundee respected each other mutually, and their relationship transcended their job: they became friends.
Dundee travelled around the world with Ali, and he was the key strategist in all of Ali's fights, which also included wins over Archie Moore, Floyd Patterson Joe Frazier, George Foreman, Ken Norton, and, later on, Leon Spinks.
After Ali's retirement, Dundee saw a future, emerging star in Sugar Ray Leonard, whom he has called a smaller version of Ali. Dundee once again led Leonard to many of his biggest wins, including the defeats of Wilfred Benitez, Roberto Duran and Thomas Hearns. In Leonard's first bout with Hearns, Dundee, thinking that his protege was behind on the scorecards, quipped the now famous words Youre blowing it, son! Youre blowing it! before the start of round 13. Leonard went on to score a fourteenth round knockout win.