He was only 15 when he did so, beating David Felix by a knockout in round two on November 22, 1989. That marked the beginning of a 39 fight win streak.
In 1990, Barrera had seven fights, including his first rise in quality opposition, when he beat veteran Ivan Salazar, by a decision in eight rounds. In 1991, he had seven more fights, beating the likes of Abel Hinojosa and Javier Susuki Diaz, among others.
Barrera began 1992 by winning his first professional title, beating Justino Suarez by a decision in 12 rounds on April 1 to win the Mexican national Jr. Bantamweight championship. Locally, he retained the title three times before the end of the year, but internationally, he had two non title fights that helped raise his ranking among the world's Jr Bantamweights; He beat Abner Barajas by a decision in ten, and former WBO world title challenger Angel Rosario by a knockout in six.
In 1993, Barrera had six fights, winning each. He outpointed Salazar in a rematch, and retained his title against Noe Santillana, among others.
By 1994, Barrera was attending school to become a lawyer. But he also kept on winning fights. On April 13, he beat future world champion Carlos Salazar by a decision in ten in Argentina. He also beat former world champion Eddie Cook before the end of the year.
Barrera began 1995 by fighting for a world title for the first time: On March 31, he became the WBO's world Bantamweight champion by beating Puerto Rico's Daniel Cobrita Jimenez by a decision in 12 rounds at Anaheim, California. By this time, many boxing experts and critics were calling Barrera Mexico's next Julio Cesar Chavez. He made four defenses before the year was over, including a two round knockout win against future world champion Frankie Toledo, a first round knockout win over Maui Diaz and a 12 round decision win over future world champion Agapito Sanchez.
1996 was an interesting year for the champion. On February 6, he fought on one of the first installments of HBO Boxing's spin-off series HBO Boxing After Dark. He was dropped by former and future world champion Kennedy McKinney, but he rose off the floor to drop McKinney five times and retain the title by a knockout in round 12 of what many observers and viewers called a classic. Then he beat former world champions Jesse Benavides and Orlando Fernandez before suffering his first loss, to Junior Poison Jones, by a disqualification in round five, losing his title and his undefeated record. While Barrera was sent to the floor in round five by what appeared to be a punch by Jones, he was declared the loser by disqualification and not by knockout because his managers climbed onto the ring to stop the fight, and WBO rules state that in such a case the loser is declared loser by disqualification.
In 1997, he was given a chance to recover his title, facing Jones in a rematch April 18 in Las Vegas. Barrera lost a close but unanimous decision, however, and retired for a short period of time after that.
He announced a comeback in 1998, and he started off by beating old rival Angel Rosario, by a knockout in round five. After two more wins, he was given another world title try, once again, by the WBO. On October 31, as part of a Halloween night themed undercard, he became world Jr. Featherweight champion by defeating Richie Wenton by a knockout in three, winning the WBO's vacant title.
In 1999, he had two title defenses and then he ran intro controversy: On December 18, he beat Cesar Najera in four rounds at California. But upon finding out that Najera was actually a Barrera sparring partner with a negative boxing record, the California State Athletic Commission decided to rule the fight a no contest instead.
Year 2000 brought a few more interesting twists to Barrera's boxing career: In March of that year, he and the WBC's world Jr. Featherweight title Erik Morales met at Las Vegas. The WBO approved of the bout as an unification bout, but the WBC, which has so far refused to deal with the WBO, did not. He and Morales fought in what Ring Magazine named their Fight of the Year for the year 2000, and what many critics also consider a classic. Barrera lost a close split decision after knocking Morales down in the final round, and the WBO shortly recognized Morales as their world champion. However, in an unprecedented move in boxing history, the WBO decided that, in their eyes, it was unjustified for Barrera to have lost that fight, and they soon reinstated Barrera as their world Jr. Featherweight champion. The rest of the year, he defended the crown three times, beating Acelino Freitas's brother Luiz Freitas by a knockout in round one, and former world champion Jesus Salud in six, in addition to a win over Jose Luis Balbuena.
Barrera once again moved up in weight in 2001, and he began by joining boxing's exclusive group of world champions in three different categories by defeating Naseem Hamed by a decision in 12 rounds on April 7.
He took a long lay-off after that, but in 2002, he met Morales in a rematch. Once again, the WBC refused to deal with the WBO and recognize the bout as a world championship confrontation, but the WBO recognized it as a world title fight. Barrera avenged his earlier loss to Morales by providing Morales with his first career defeat, winning another close 12 round decision. In his next defense, he met old friend and former world champion Johnny Tapia on November 7 and beat Tapia by a 12 round unanimous decision.
Barrera dropped from law school recently. There are talks currently about a third bout with Morales or a rematch with Hamed. In the meantime, he got his 60th career win on April 12 of 2003, defeating former world champion Kevin Kelley by a knockout in round four to retain the WBO's world Featherweight title. Barrera then lost, on November 15, by knockout in round eleven to former world Jr. Featherweight champion Manny Pacquiao, in San Antonio, Texas.
He is managed by Ricardo Maldonado, who also manages Puerto Rican world champion boxers Alex El Nene Sanchez and Daniel Santos.
His record consists of 60 wins, 4 losses, and 1 no-contest, with 40 wins by knockout.