Berlusconi's coalition snatched four regions from the center-left in what was widely viewed as a major test of the prime minister's popularity among voters.
The center-right held on to the only two regions it had governed, Veneto and Lombardy, and gained control of Piedmont in the north, Lazio in central Italy and Campania and Calabria in the south, the Italian news agency ANSA reported.
Election officials said 64.2 percent of the more than 41 million eligible voters cast ballots -- down from 72 percent in regional elections in 2005.
In that race, the center-right had lost six of eight regions it held, while the center-left gained strength.
In the voting Sunday and Monday in 13 of Italy's 20 regions, the center-left held on to Liguria in the north, the central regions of Emilia Romagna, Tuscany, Marche and Umbria and the southern regions of Puglia and Basilicata.
The center-right's gains surprised some observers after a recent ANSA poll showed approval for scandal-plagued Berlusconi, his government and his People of Freedom party had fallen to an all-time low.
In July, Berlusconi admitted spending a night with an escort, saying, "I'm no saint," but denied paying for sex.
In June, the 71-year-old billionaire denied allegations he paid prostitutes to attend parties at his official residences while photos showed a topless woman and a naked man at his Sardinia villa and a celebrity using the prime minister's official jet, the BBC said.
That came the month after his wife said she was divorcing him because he attended the 18th birthday party of a "female friend."