Leonard won gold at the 1976 Summer Olympics in Montreal, Canada. Sugar Ray wanted to go to Harvard and become a lawyer, but he was convinced to do otherwise by boxing promoters, being offered $500,000 for his first professional fight against tough Puerto Rican Luis Vega. The fight was televised nationally, and Leonard could display his talents, winning a 6 round decision.
Leonard built a string of wins until he was able to challenge world welterweight champion Wilfredo Benitez. Among his first opponents were top contenders Andy Price and Marcos Gerardo. He and Benitez met in the Caesar's Palace in Las Vegas on November 3, 1979 and after a brilliantly fought battle, Leonard was declared world champion for the first time with a technical knockout in round 15, with 6 seconds left in the fight.
Leonard won his first defense in spectacular fashion, knocking out British challenger Dave Green in 4 rounds in Landover, Maryland. Green was frozen with a right to the chin. The fight was broadcast to a national audience in the United States. Next, Leonard went back to the Olympic Stadium in Montreal to defend his title against Roberto Duran, in the first superfight of the 1980s. Leonard fell prey to Duran's mental tactics and fought Duran's fight, although it can be said he almost beat Duran at his own game. But Duran etched out a close but unanimous decision, inflicting Leonard his first loss.
Leonard came back for their rematch in New Orleans on November 25, 1980, a new man with a new plan. He outboxed Duran, frustrating him from the opening bell, and with 17 seconds to go in round 8, the unthinkable happened: Duran turned around, walked to his corner and gave up, saying the now worldwide famous words of no más. Referee Octavio Meyran, perhaps incredulous as was the rest of the world of what he was seeing, asked Duran if he was sure, and Duran repeated himself again: No más, no más.
Leonard was a world champion again and, after avenging his only defeat, once more on top of the world.
Next came his fight with Ayub Kalule, world junior middleweight champion. Kalule gave Leonard a tough fight and it was closely contested, but in round 9, Leonard connected a huge right to the chin that sent Kalule down. He was stopped in that round, and in celebration of his second world title, Leonard did a back flip.
Friend and ring arch-rival Thomas Hearns, meanwhile, was tearing apart the Welterweight division and had won the WBA world title knocking out the Hall Of Famer, Pipino Cuevas. A unification bout was set for September 16, 1981, once again at the Caesar's Palace hotel. In a bout showcased by HBO, Leonard and Hearns fought one for the ages. Superfight 1981, was full of surprises, as after starting out banging, Hearns decided to change from puncher to boxer from round 6 onward, with Leonard also trading roles, from boxer to puncher. With an eye completely closed, trailing on all 3 score cards, Leonard nonetheless started closing the gap until he floored Hearns twice in round 13, the second one almost causing Hearns to fall out of the ring. The spent Hearns could barely get up for round 14, and after a rain of punches caught him against the ropes, referee David Pearl had no choice but to stop the fight, making Leonard the undisputed world welterweight champion.
Defenses against Larry Bonds and Bruce Finch followed, but his next defense, vs Roger Stafford, had to be postponed. Doctors discovered Leonard had suffered a detached retina, and he underwent surgery at Johns Hopkins hospital in July 1982 to repair the problem. By then people were constantly talking about a fight with world Middleweight champion Marvin Hagler.
Leonard decided to take a job as a commentator with HBO, and a few months after pondering his future, he invited Hagler and other boxing dignataries to an event in Washington D.C, where he announced his retirement. Hagler left the conference disappointed, and Leonard, who said "Unfortunately, that fight (vs Hagler) will never happen", would later learn to never say never again.
In 1984, after media darling Leonard had spent part of 1983 announcing such enterprises as Golden Skillet chicken and Franklin sporting goods, he announced a comeback. With Hagler in attendance, Leonard was dropped for the first time in his career, by journeyman Kevin Howard, and although he got up and scored a 9 round technical knockout win, in the press conference after the fight, he announced that he would go back into retirement.
1983 saw the creation of the Sugar Ray Leonard network, a short-lived tv station from Maryland commandeered by Leonard and dedicated to 24 hour boxing news, interviews and fights.
1986 came, and rumors surfaced that Leonard was training again and considering a fight with Hagler. It was a given by many boxing fans that Hagler would easily manage the laid off boxer, who had not been at his best in his last fight 3 years before. But once again, Leonard surprised the experts in their April 6, 1987 fight, hanging on to win a controversial split decision to become the world's middleweight champion, and the boxer who came back after the longest lay-off in history to win a world title in his first fight back.
Leonard went up in weight again on November 7, 1988 and came off the canvas to win two world titles the same night, the vacant world Super Middleweight championship, and Don Ladonde's world light heavyweight championship, knocking Ladonde out in the ninth round, and then in 1989 he embarked on a trip that would take him through two meetings with old enemies. He met Hearns again at Caesar's Palace and had to endure two falls and a rocky start to pull out a twelve round draw, and then five months later, patiently fought Roberto Duran for a third time, at the Mirage hotel, also in Las Vegas, winning a twelve round unanimous decision.
Leonard then retired, but true to his fashion, came back in 1991, to try his fortune with world junior middleweight champion Terry Norris at the Madison Square Garden, Leonard's first outing there. Leonard suffered two knockdowns but lasted the distance and was respectful in defeat.
Ahead were very difficult times: after the fight, Leonard admitted to a stint with cocaine that lasted from 1984 to 1989. He fell victim to the drug, and reports surfaced of violence against his wife Juanita. Leonard admitted that his problems were caused by a need to be involved in the sport of boxing during the periods he was away from it, and inmaturity. He kicked his habit for good after 1989.
He and Juanita later divorced, and Leonard tried to embark on another comeback. This time, his opponent, Hector 'Macho' Camacho was too fast and powerful for him, making Leonard suffer his only knockout loss, in the 5th round. For Leonard, it was finally enough, and he has not fought since.
Leonard is now the head of a budding boxing promotion company that includes the likes of Camacho's son, 'Macho' Camacho Jr, world cruiserweight champion Vassiliy Jirov and former world middleweight champion James Toney.
He is a member of the International Boxing Hall Of Fame.