The unbeaten five-division champion is trading a life in a posh five-bedroom home for almost three months in a cell about one-third the size of a small boxing ring.
Mayweather pleaded guilty to misdemeanor domestic battery charges stemming from an incident two years ago, when he pulled the hair and twisted the arm of Josie Harris, the mother of three of his children. The younger two children watched the abuse while the older child ran out of a back door to fetch a security guard.
Prosecutors dropped felony and misdemeanor charges that could have gotten Mayweather 34 years in prison if he had been convicted on all counts.
In January, a judge allowed Mayweather to postpone his jail sentence so he could fight Miguel Cotto in Las Vegas May 5. Mayweather won that bout, guaranteeing him $32 million. Cotto was paid $8 million.
As a high-profile inmate, police say the 35-year-old will likely serve most of his time in a small solo cell. There is floor space for sit-ups and push-ups, but Mayweather's stint in the high-rise Clark County Detention Center is expected to limit his ability to train for another fight.
Mayweather's jail stay will be capped at 87 days, because the judge gave him credit for three days previously served. It could be reduced by several weeks for good behavior, officials said. He was also ordered to complete a yearlong domestic violence counseling program, 100 hours of community service and pay a $2,500 fine.
Harris and the three children now live in Southern California.
The Associated Press contributed to this report.