Analysts said a strong lead in both houses of parliament would allow Berlusconi more flexibility to carry out economic and social reforms he promised.
Once in office for the third time, Berlusconi will face an imminent task of saving a sluggish economy from recession, a major concern weighing heavily on most voters.
The Italian economic growth has been under potential in recent years. In 2007, it was 1.5 percent, far below the eurozone average of 2.7 percent.
The 2.4-trillion-U.S. dollar economy was projected to grow just 0.3 percent this year, according to a forecast by the International Monetary Fund earlier this month, the slowest among the more than two dozen "advanced economies."
To save the stumbling economy, both Berlusconi and Veltroni made similar pledges like lowering taxes and cutting public spending.
Italy wrapped up a two-day election earlier Monday, in which voters cast their ballots to decide the new national parliament and who will govern their country in the next five years.
Of Italy's 58.2 million population, 47.3 million are eligible to vote for 630 member in the lower house and 43.2 million can vote for 315 elected members in the Senate.
Under Italy's electoral system, voters cannot choose each parliamentarian candidate, but select from lists headed by 32 hopefuls for prime minister, of which 71-year-old media Berlusconi and 52-year-old central-leftist Veltroni were the two main contenders.
Born in Milan in September 29, 1936, Berlusconi was elected prime minister for the first time in 1994, shortly after he founded his own center-right party.
In the 2001 elections, Berlusconi won the second term, but lost the April 2006 general election to Prodi.
Amid years of political instability and a sluggish economy, Italian voters seemed to be losing appetite for politics as less people went to polls this time.
Official figures from the Interior Ministry showed 80.5 percent of eligible voters cast their ballots for the lower house and the turnout for the election of the Senate stood at 80.4 percent. Both were lower than the 83.6 percent turnout registered two years ago.