The 72-year-old former world heavyweight champion was hospitalised on Saturday, although spokesman Bob Gunnell stressed his condition was not serious.
A further release on Monday revealed Ali, who suffers from Parkinson's disease, has experienced significant improvements in his health and is likely to leave hospital in the near future.
"Boxing legend Muhammad Ali has vastly improved since being admitted to the hospital over the weekend with a mild case of pneumonia," read a statement from Gunnell.
"Ali’s team of doctors hopes to discharge him soon.
"The Ali family continues to request privacy and appreciates all of the prayers and well wishes."
Ali is a three-time world heavyweight champion and also won an Olympic gold medal in the 1960 Games in Rome.