The bill was passed with a 27-vote majority on Tuesday, in the face of stiff opposition from centre-left leaders.
Several media outlets, including state broadcaster RAI, have also criticised the move.
Berlusconi is said to have some kind of control over an estimated 95% of Italian TV.
The new law, named after Communications Minister Maurizio Gasparri, will allow the Berlusconi family's holding company to buy into radio and newspapers from 2009.
The government had said it would change media laws when it took office in 2001, but unveiled the package only in September last year, following lengthy consultations.
Those in favour of the bill argue that it will inject life into the rigid media market, making the protected industry robust enough to take on foreign networks.
Berlusconi to gain?
However, detractors say it favours private broadcaster Mediaset, top publisher Mondadori and Italy's biggest advertising sales firm - all controlled by the Berlusconi family holding company Fininvest.
"From today we are all a little less free... the law worsens all the ills of our television system: little competition, falling quality and progressive restriction of pluralism," said Paolo Gentiloni of the centre-left opposition Margherita party.
"From today we are all a little less free... the law worsens all the ills of our television system: little competition, falling quality and progressive restriction of pluralism"
Margherita party leader
"We are satisfied. But it's only a chapter in a never-ending story," Mediaset chairman Fedele Confalonieri told reporters in Monte Carlo.
Earlier, he said the law would give Mediaset and publisher Mondadori access to extra revenues of $896 million.
The relaxing of media ownership laws is seen as following the trend in Britain, Spain and the United States.
US legislators last week agreed to allow increased control of the airwaves by television networks, while Spain is considering allowing one firm to hold stakes in more than one network.
Expanding ad market
However, experts point to the Berlusconi angle in the Italian media industry. "From a media ownership point of view, what Italy is trying to have is a system that is not greatly different from Britain's. But then there's the Berlusconi factor," said a London-based analyst.
"Having a prime minister whose family has a chunk of a broadcaster that has 65% of the advertising market and 43% audience share makes the two systems incomparable," the analyst added.
The Gasparri law expands the advertising market by allowing more space for commercials within shows - increasing time beyond the current 20 minutes every hour.
The law also puts RAI through a privatisation that critics, including its president Lucia Annunziata and other media executives, have called "fake", because it allows shareholders
to take just a 1% stake in the state broadcaster.
Annunziata said she would resign if the bill was passed.