Bob Gunnell said in a statement on Thursday that the 74-year-old Ali had experienced difficulty breathing but was already receiving treatment at a medical facility here, reports Efe.
Ali, who has suffered from Parkinson's disease for decades, has spent most of his time in recent years at his residence here because that city's warm climate makes it easier for him to manage the illness.
Gunnell said Ali was not in serious condition, adding he was hospitalised as a precautionary measure and that his stay was expected to be brief.
"He's being treated by his team of doctors and is in fair condition," Gunnell said in the statement.
"A brief hospital stay is expected. At this time, the Muhammad Ali family respectfully requests privacy," the spokesman added.
Gunnell provided no details on the type of treatment Ali was receiving.
Considered by many to be the greatest heavyweight in boxing history, Ali has remained active in charity programs and continued to travel internationally despite his health problems.
His last public appearance was in April at an event to raise funds for charitable organisations in Arizona.