He is the first Mexico-born boxer in history to win world championships in four weight classes, ranging from super bantamweight to light welterweight.

Morales defeated fifteen world champions during the course of his career, and is famous for his trilogies with fellow Mexican legend Marco Antonio Barrera, as well as Manny Pacquiao.

Under the tutelage of his father, José Morales, a fighter himself, Erik started boxing at the age of five and amassed a very impressive amateur career that totaled 114 fights (108–6), winning 11 major titles in Mexico in the process.

On September 6, 1997, in El Paso, Texas, at the age of 21, he won his first world title by stopping WBC Super Bantamweight Champion and now member of the International Boxing Hall of Fame, Daniel Zaragoza, via knockout in eleven rounds.

In February 2000, Morales defeated Marco Antonio Barrera to win the WBO Super Bantamweight title, in a fight that is now considered one of boxing's classics.

Morales bounced back with a dominating twelve-round decision victory over former world champion, Paulie Ayala in November 2002 to regain the vacant WBC Featherweight title.

All the fighters on the card donated their purses to "Vamos Mexico," a children's charity headed by Marta Sahagun, wife of Mexican president Vicente Fox.

In October 2003, Morales defeated Guty Espadas Jr. in a rematch of their first close fight, which was also a WBC Super Featherweight title eliminator.

With the victory he became the second Mexican boxer to win a title at three separate weight divisions, the first being the acclaimed Julio César Chávez.

On July 31, 2004, Morales unified his WBC Super Featherweight title with the IBF version by way of a twelve-round unanimous decision over Carlos Hernández.

On March 19, 2005, as a betting underdog, Morales defeated then three-division world champion Filipino boxer Manny Pacquiao, by a unanimous decision.

During the 12th round, Morales, comfortably ahead on the scorecards, decided to brawl with the Filipino slugger, even turning southpaw during the process.

Later that night, at the post-fight press conference, Erik further explained his reasoning for brawling with the Filipino slugger; "It was a great pleasure to fight this way.

He also expressed his desire to become the first Mexican fighter to win four WBC titles in different divisions and surpass Julio César Chávez's record by campaigning at the lightweight class of 135 lb (61 kg).

[13] On August 4, 2007, Morales fought David Díaz for the WBC Lightweight title and lost a close unanimous decision at the Allstate Arena.

[14] In various interviews conducted in 2009, Morales began to state that he would fight again in late 2009 to early 2010, after he gave his body enough time to rest.

Many boxing pundits felt that an aging Morales, fighting a couple of divisions above his best weight, stood little chance against the hard hitting Maidana.

Morales' eye was badly swollen in the first round by a series of hard shots, especially a devastating uppercut, and it looked like the rout was on.

Morales put up a valiant effort, performed better than anyone thought possible, won the crowd over and gave the boxing public another "Fight of the Year" candidate.

Morales was due to fight WBO Inter-Continental Light Welterweight Champion Lucas Matthysse as an undercard to the Floyd Mayweather Jr. vs. Victor Ortiz bout.

On September 17, 2011, Morales won the WBC Light Welterweight Championship with a win over un-rated Pablo César Cano.

The title had been vacant after previous champion Timothy Bradley's status had contentiously been changed to Champ in Recess due to inactivity.

On March 24, 2012, Morales faced 23-year-old Danny García (22–0 14 KO's) in another chapter of the storied "Puerto Rico vs. Mexico" boxing rivalry.

Morales fought on October 20, 2012, on a rematch with now The Ring, WBC & WBA (Super) Light Welterweight Champion Danny Garcia.

Prior to Morales-Garcia rematch on October 20, 2012, United States Anti-Doping Agency (USADA) conducted two random drug tests (Oct 3 and 10, 2012).

Morales was tested positive for use of the banned substance Clenbuterol, a weight-loss drug, it reduces fat deposits and is believed to increase muscle mass.

Although the New York State Athletic Commission was notified 24 hours in advance of the Garcia-Morales bout regarding Morales’ positive drug test results, the legal process was still ongoing.

“(The party is) not only for me, but for the people who stood by me – my father, my mother, my brothers, the fans, the press, especially the coaches, trainers, doctors, sparring partners and all of those who helped prepare me and demanded me to be better every day.

Erik Morales currently spends his time managing a $3.5 million budget running the parks and recreation department in Tijuana.

"[20] On May 30, 2015, Morales agreed to train former light welterweight champion Jessie Vargas for his then-upcoming fight with Timothy Bradley.