He was in a cardiac unit at Milan's San Raffaele Hospital after reportedly suffering breathing problems.
The 86-year-old billionaire media tycoon has suffered repeated bouts of ill-health in recent years and came out of hospital just last week.
“He has been admitted to intensive care because a problem caused by an infection has not been resolved but he is speaking,” Foreign Minister Antonio Tajani, a long-time ally of Berlusconi, told reporters in Brussels.
A source from the San Raffaele confirmed that Berlusconi was being treated in the intensive care section of its cardiothoracic wing and would remain in hospital overnight.
His eldest daughter Marina Berlusconi and his brother Paolo Berlusconi visited him during the day, Italy's Ansa news agency reported.
Berlusconi's Forza Italia party is part of Prime Minister Giorgia Meloni's right-wing coalition although he does not have a role in government.
Berlusconi built Italy’s biggest commercial television network and gained an international profile as owner of European football champions AC Milan.
He entered politics in 1994 when the previous political class was brought down by a corruption scandal.
Over time, his health has deteriorated with Berlusconi needing heart surgery in 2016.
He has also had prostate cancer.
The former prime minister has been repeatedly admitted to hospital over the past couple of years after contracting COVID-19 in 2020.
Italian media reports said Berlusconi was taken to hospital after complaining of breathing difficulties.
Three sources from Forza Italia said he was in intensive care, and one of them confirmed reports that he was being treated in a cardiac unit.
Another of the sources said the situation was “under control”.
Berlusconi stepped down as prime minister for the last time in 2011 as Italy came close to a Greek-style debt crisis.
He had also been weighed down by his own scandals, including his notorious “bunga bunga” parties.
He was returned to the Senate of the Italian parliament after a general election last September.
AAP
