The former world boxing champ walked down the aisle at the Las Vegas Hilton at a low key ceremony with no guests. A spokesperson for the hotel's chapel said the couple appeared "very happy and sincere". It is the former boxer's third marriage. He was formerly married to actress Robin Givens - in 1988 - and to Dr Monica Turner in 1997.
Local marriage records show Mike and his 32-year-old girlfriend applied for a marriage licence about 30 minutes before they took part in the ceremony.
The bride, who has known Mike for ten years, was wearing what the chaplain who performed the ceremony described as "appropriate dress" rather than a wedding gown and the couple asked for a simple ceremony with "nothing special".
Last month the boxer's daughter Exodus died following an accident at the family home in Phoenix, Arizona. The four-year-old was rushed to hospital after she was found with her neck caught in the cable of a treadmill exercise machine.