The 89-year-old Spaniard, who headed the IOC from 1980 to 2001, was attending the Sportel international sports television festival. He was treated at the Princess Grace Hospital Centre in Monaco.
"It was a slight reaction to fatigue without importance and now he's resting in his hotel," Samaranch spokeswoman Annie Inchauspe told Spanish news agency Efe, denying reports on L'Equipe's Web site that he had a mild heart attack. "He was only in the hospital for some minutes."
IOC spokesman Mark Adams said he had no information about a heart attack, and that Samaranch had gone to the hospital for "a minor ailment."
Earlier this month, Samaranch was in Copenhagen to push Madrid's unsuccessful bid to host the 2016 Olympics. The Spanish capital lost to Rio de Janeiro in the final round of the vote.
Samaranch, succeeded as IOC president by Jacques Rogge, spent two days in a Madrid hospital two years ago after a dizzy spell. He was hospitalized in Switzerland in 2001 for "extreme fatigue" and in Barcelona for high blood pressure. He has also received regular dialysis treatment for kidney trouble.
As honorary IOC president for life, Samaranch has continued to attend IOC meetings.