On his 7th fight, Barrera won the WBA Fedelatin and the interim WBO Latino light heavyweight titles.

Barrera was ranked by the WBA and the WBC as one of the top 15 light heavyweight contenders early in his career.

In December 2015, Barrera faced Karo Murat in an IBF eliminator, the winner was to become Sergey Kovalev's mandatory challenger.

[4] The IBF had previously ordered Barrera to fight Artur Beterbiev and Igor Mikhalkin but negotiations for both of those bouts fell through.

Barrera and Kovalev were both signed to Kathy Duva's promotional outfit at the time, Main Events.

En route to a wide unanimous decision victory, Ward dropped Barrera to the canvas in the third round as he turned a left hook while on the ropes.

Ward dictated the pace for the vast majority of the bout, showcasing good strength and ring generalship against Barrera.

The latter would return the favour in round 2, dropping Barrera with a combination of punches following a check left hook.

Early reports indicated the fight would be part of a HBO triple-header also featuring Miguel Berchelt defending his WBC super featherweight title against mandated Takashi Miura on 15 July 2017 in Inglewood, California.

At first the HBO commentary thought the referee had made a mistake, but were later told, both fighters agreed to the fight being 10 rounds.

[18] A few days later, Smith released a statement on social media that he had broken his jaw and believed to have broken it in round two, “Somewhere during the second round I was injured and was in a lot of pain, but I did not want to let it show and I refused to quit.” As the fight went on, he admitted the pain got worse and the fight got tougher.

[26][27] In his next fight, Barrera fought for a world title for the first time in his career, against WBA light heavyweight champion Dmitry Bivol.

Bivol dominated throughout the fight, which culminated in a big right hand to Barrera's temple in the final round that dropped the Cuban boxer.

It was a one-sided victory for the Cuban, who won convincingly on all judges' scorecards, 99-91 twice and 98-92, while also hurting and bloodying Monaghan in the process.

[29] On 15 June 2019, Barrera fought Jesse Hart, who had moved up to light heavyweight prior to the fight.

Barrera managed to land clean shots throughout the fight, but Hart, despite his technical flaws, did enough in the eyes of all three judges to win the bout, while also scoring one knockdown in the process.