The 40-year-old American described his opponent as a "tough competitor" and admitted that he exceeded his expectations in the boxing ring.
"He is a tough competitor," BBC Sport quotes Mayweather as saying. "He was a lot better than I thought. But I was the better man.
"I guaranteed everybody this would not go the distance. Boxing's reputation was on the line."
McGregor landed a number of early blows in the opening rounds, but referee Robert Byrd brought the contest to a close in round 10 as the UFC man struggled against fatigue.
Mayweather will return to retirement with a 100% record in 50 professional bouts.