Opponents want Berlusconi to pick business or politics
Opposition lawmakers walked out of Italy's lower house of parliament in protest at the bill which they called toothless.
The measures - aimed at resolving any conflict of interest between the prime minister's private and public roles - passed with 308 votes in favour, two abstentions and, in the absence of opposition MPs, none against.
The bill will now be sent to the Senate, where there is also a large majority for the party of Mr Berlusconi, who is Italy's wealthiest businessman with assets worth more than $10bn.
The three-day debate began with an almost empty Chamber of Deputies but developed into rowdy exchanges and actual scuffles between government and opposition MPs.
"We shall have to give our opposition a lesson in democracy," Mr Berlusconi said.
The government-sponsored bill says holding public office is incompatible with running a company, but not "mere ownership of a private company or of a company stake or its shares".
Centre-left opposition MPs said the measure appeared tailor-made to fit Mr Berlusconi. His empire includes Italy's largest private broadcaster, film and advertising companies, investment and insurance concerns, publishing and real estate.
The new law would mean that Mr Berlusconi's two elder children, who are in nominal charge of running his business empire, could not be appointed government ministers - an extremely unlikely occurrence.
Mr Berlusconi himself may only have to divest himself of the presidency of the AC Milan football club.
Sanctions 'unnecessary'
An opposition leader, Luciano Violante, said the walkout was intended to be a dramatic defence of "freedom, democracy and pluralism".
Before the vote, MP Pietro Folena said: "It's a grotesque, grave, paradoxical law."
Public Functions Minister Franco Frattini, who wrote the legislation aimed at senior politicians, insisted sanctions were not needed because any minister caught with a conflict of interest would probably resign out of political embarrassment.
The BBC's Rome correspondent David Willey said the law was unlikely to defuse unease among Italians about Mr Berlusconi's apparent belief he is above the law.
Mr Berlusconi is being prosecuted for allegedly bribing a judge but claims he is the victim of a vendetta by left-wing judges.