The Court of Cassation said Prodi won the lower house of parliament by a margin of 24,000 votes over Premier Silvio Berlusconi's conservatives — a margin virtually unchanged from the one previously announced.
After the results were announced, Prodi said Italians should have no more doubts about his win in the April 9-10 vote.
"Finally the electoral affair is over," Prodi said. "Italians have no more doubts about our victory."
"We are aware of the rifts and the divisions that we will have to heal, as we are aware of the problems and difficulties we will have to face."
Prodi said he had not received a phone call from Berlusconi.
Thank to a majority bonus aimed at increasing governability, Prodi's coalition is assigned 55 percent of the seats in the lower house, regardless of the vote gap.
Berlusconi won the popular vote for the Senate, but Prodi gained a two-seat majority due to a complicated system of regional bonuses.
Still, a top Berlusconi ally said the conservative coalition was not conceding defeat.
The announcement "does not exhaust all the checks on the electoral results," Giulio Tremonti, the economy minister, was quoted as saying by the ANSA news agency.
The court reviewed some 2,100 ballots for the lower Chamber of Deputies that were not immediately included in the overall count because the voting intentions were unclear.
In the Senate, there were another 3,100 contested ballots, but they were not expected to change the outcome. Preliminary reports by regional offices confirmed the outcome of the vote.
The Interior Ministry reduced the number of contested ballots last week — from a combined 80,000 for both houses to a combined 5,200 — boosting the likelihood that Prodi's victory would stand.
Prodi won a razor-thin majority in the election, which brought 40 million Italians to the polls.