Mayweather, 38, easily out-boxed his younger opponent over the 12 rounds to retain his WBC and WBA welterweight titles and improve his perfect career record to 49-0, matching the benchmark set by former heavyweight champion Rocky Marciano.
Dominating most of the exchanges, Mayweather beat Berto, who dropped to 30-4 as he suffered his fourth loss in his last seven fights at the MGM Grand Garden Arena in Las Vegas.
“It was a good fight. I knew he would be a tough competitor. Experience played a major role tonight. What can I say? I was the better man tonight,” Mayweather said in a ringside interview.
Asked if he might be tempted to come back for a 50th fight, Mayweather replied: “My career is over. It’s official.
“You’ve got no one to hang it up, so I think it’s about time for me to hang it up. I’m not going to be doing it now. I’m close to 40 years old, I’ve been in this sport 19 years, been world champion for 18 years, I’ve broken all records.
“There’s nothing left to prove in the sport of boxing.”