Exit polls give the conservative media mogul's People of Freedom party 40%-44% of the vote against 38-42% for center-left rival Walter Veltroni in the lower house, and a similar margin in the upper house.
Berlusconi, 71, controls most of Italy's media through his company Mediaset.
Veltroni, a former mayor of Rome, succeeded former premier Romano Prodi as leader of Italy's Democratic Party after Prodi resigned three months ago following the collapse of his center-left parliamentary coalition.
The election winner will face a major challenge in turning round Italy's economic slowdown, with the International Monetary Fund projecting almost zero growth for Italy this year. Both candidates have pledged to reduce the national debt, one of the world's largest, while cutting taxes.
