Since his professional debut in 2004, Berto has become known for his toughness, formidable punching power, and fast hand speed. In the late 2000's he was considered a rising star in the welterweight division, as well as a highly regarded young prospect in boxing. He reached the peak of his career in 2011, holding the WBC welterweight title which he had won in 2008 and made five defenses and was ranked as the world's third best welterweight, behind the then-top stars Manny Pacquiao and Floyd Mayweather Jr.
Berto's success was cut short after his first career loss to Victor Ortiz in 2011, which won Fight of the Year honors by The Ring magazine. Since then, Berto's career has fluctuated: from 2012 to 2015 he suffered three further losses, but bounced back in 2016 with a win over Ortiz in a rematch.
Berto vs. Zaveck
On September 3, 2011, Berto returned after his defeat to Victor Ortiz to face IBF welterweight champion and Ring Top 10 welterweight Dejan Zavec. After 5 rounds of a closely competitive fight, Zaveck's corner stopped the fight as he had been cut. The two men embraced and Berto thanked the Slovenian fans for traveling over to America to cheer their countryman on. Berto called his performance "so-so," becoming a two-time world champion and the new IBF welterweight champion.
Berto relinquished his IBF welterweight title rather than face mandatory challenger Randall Bailey in order to facilitate the rematch with Ortiz because he wanted the opportunity to avenge his only defeat (at the time).
After testing positive for a banned substance, the rematch against Oritz planned for June 23, 2012 was cancelled. It has since been ruled that Berto's positive test was the result of contamination, and Berto regained his boxing license. Josesito Lopez replaced Berto and fought Oritz on the scheduled date at the Staples Center in Los Angeles. Lopez stopped Ortiz after 9 rounds claiming the vacant WBC silver welterweight title.
Berto vs. Guerrero
Berto's next fight was scheduled for November 24, 2012, in Ontario, California. The opponent was Ring Top 10 welterweight and WBC Interim welterweight champion Robert Guerrero. Berto was knocked down twice early in the fight but came back well to give Guerrero a tough scrap, but Guerrero managed to narrowly maintain control and won via unanimous decision. Both of Berto's eyes and Guerrero's right eye were closed shut by the end of the fight.
Following an 8-month lay-off after losing to Guerrero, Berto eventually returned to the ring to face Jesus Soto Karass on July 27, 2013, at the AT&T Center in San Antonio. In a tough, entertaining back-and-forth fight, Berto lost via TKO in the twelfth round after having put Soto Karass on the canvas in the previous round. At the time of the stoppage, one judge had Berto ahead in the fight 105-103, one had him behind in the fight 103-105, and the other judge had the fight even at 104-104.