Mr Berlusconi is likely to appeal and will remain free in the meantime.
He is presently appealing against a tax-fraud conviction and also faces a verdict in a sex trial later in March.
The tax fraud conviction stems from a trial last October that saw him sentenced to a year in jail.
The sex trial concerns allegations that he paid for sex with an underage prostitute.
The BBC’s Alan Johnston in Rome says there is no real prospect of Mr Berlusconi going to jail over the wiretap case, but the conviction is another very serious blow to his reputation.
It comes weeks after his right-wing coalition did better than expected in a general election that provided no clear winner.
However, his coalition looks to be on the margins of efforts to form a new government, and the outcome of this court case is unlikely to have any direct bearing on those negotiations.
The other faction leaders have long had utter contempt for everything Mr Berlusconi stands for, and this verdict will only serve to entrench their views, our correspondent adds.
Prosecutors brought the wiretap case after a transcript of a phone conversation intercepted by the authorities was published in the newspaper Il Giornale, owned by Mr Berlusconi’s brother Paolo.
The conversation took place between the head of insurer Unipol and Piero Fassino, who was the leader of the biggest centre-left party and Mr Berlusconi’s biggest political rival at the time.
Unipol was trying to take over BNL bank in 2005. Magistrates had ordered the wiretap as part of an investigation into inappropriate interference in the takeover.
The publication of the transcript in a national newspaper broke secrecy rules, and Mr Berlusconi was accused of obtaining the transcript from the wiretap company used by magistrates.
He was convicted of breaching confidentiality.
His brother Paolo was convicted of the same charge and jailed for two years and three months.
Analysts say wiretapped conversations are widely published in Italian media, despite the risks of prosecution.
In numerous trials over the years, Mr Berlusconi has been accused of charges including accounting fraud, perjury, bribery, corruption, having unlawful sex with a minor, and fraud over the sale of film rights.
Mr Berlusconi says he is the target of a vendetta by politically biased prosecutors. He has denied all the accusations against him and has either been acquitted or let off under statutes of limitations.
Reprinted from BBCnews