Double pneumonia affects both lungs and can make breathing difficult.
The 83-year-old was taken to Milan's San Raffaele hospital Thursday night, two days after his political party announced he had contracted coronavirus.
CORONAVIRUS IN THE US: STATE BY STATE BREAKDOWN
Double, or bilateral, pneumonia has been seen in many patients hospitalized with COVID-19.
Berlusconi's political party Forza Italia said in a statement that his condition was "not a cause for concern."
Sky Italia television reported the octogenarian was not in intensive care.
MODEL IN SILVIO BERLUSCONI BUNGA BUNGA TRIAL HAD HIGH LEVELS OF HEAVY METALS IN BODY WHEN SHE DIED, PROSECUTORS SAY
Alberto Zangrillo, who works at San Raffaele hospital, where Berlusconi was taken, told reporters that test results are reassuring and “make us optimistic” for his recovery over the next “hours and days.”
Italy's former Italian prime ministe was accused in 2012 of paying for sex with an underage woman at sex-fueled “bunga bunga” parties and wielding his power in an attempt to cover it up.
He was found guilty, but the conviction was overturned on an appeal.
Berlusconi was ultimately convicted on tax fraud charges and sentenced to community service.