After winning several more amateur titles in the following years, Lennox Lewis traveled to Seoul, South Korea, for the 1988 Summer Olympics and achieved his goal. In the gold medal final, Lewis defeated Riddick Bowe with a second round referee stopped contest (RSC). Lewis became the first super heavyweight gold medallist to become world heavyweight champion as a professional. In the Games' closing ceremony, Lewis was Canada's flag bearer. Lewis became the first Canadian to win boxing gold in 56 years.

Lewis, upon turning professional, registered and amateur record of 85-9. HBO Boxing credited him with a shorter amateur record of 75 wins (58 by knockout) and 7 losses. Of all losses on the record, Valeriy Abadz of the Soviet Union was the only opponent to stop Lewis in amateurs, in October 1986.

After winning the Olympic gold, Lewis was approached immediately by big-time American boxing promoters, including Bob Arum. However, he was not overly impressed by their contract offers and thought about signing a professional contract with a Toronto based promotion group. "I feel like a basketball player being scouted by scouts down in the States. I don't want anyone controlling me. These (offers) coming to me after the Olympics are mainly because I won the gold."

Regaining the WBC title

In his comeback fight, Lewis was given a chance to fight for the mandatory challenger position within the WBC and won it by knocking out American contender Lionel Butler. However, at the behest of promoter Don King, the WBC bypassed him and gave Mike Tyson the first chance at the title recently won by Briton Frank Bruno form Oliver McCall. Bruno had previously lost to both Lewis and Tyson.

Lewis had the number 1 contender's slot in the WBC rankings when he knocked out Australian Justin Fortune, then defeated former WBO Champion Tommy Morrison in October 1995, followed by Olympic gold medallist and former WBO champion Ray Mercer in a close majority decision in May 1996. Lewis successfully sued to force Tyson to make a mandatory defence of the WBC title against him. Lewis was offered a $13.5 million guarantee to fight Tyson to settle the lawsuit, but turned it down. This would have been Lewis's highest fight purse to date. Lewis accepted $4 million from Don King to step aside and allow Tyson to fight Bruce Seldon instead, he would fight Lewis next. After winning the WBA title from Seldon, Tyson relinquished the WBC title to fight Evander Holyfield instead. The WBC title was declared vacant. This set up a rematch between Lewis and McCall, who met on 7 February 1997 in Las Vegas for the WBC title.

In one of the strangest fights in boxing history, McCall, who had lost the first three rounds, refused to box in the fourth and fifth rounds. He then began crying in the ring, forcing the referee to stop the fight and award Lewis the victory and the title. As newly recrowned WBC champion Lewis successfully defended the title in 1997 against fellow Briton and former WBO world champion Henry Akinwande, who was disqualified after five rounds for excessive clinching. Lewis then met Poland's Andrew Golota, whom he knocked out in the first round. Lewis retained the WBC world title in 1998 when he knocked out lineal champion Shannon Briggs, who had recently outpointed George Foreman in a controversial fight to win the lineal title in five rounds, and beat formerly undefeated European champion Zeljko Mavrovic from Croatia in a 12 round unanimous decision. Lewis stated in 2006 that his fight with Mavrovic was the most awkward win of his career.