The alliance between the anti-establishment Five Star Movement and right-wing Lega gained the Senate's endorsement thanks to 171 votes in favor, 117 against and 25 abstentions.
The Italian parliamentary election was held on March 4 and resulted in the M5S securing more than 32 percent of the vote.
The center-right coalition, consisting of the Lega party, Forza Italia and the Brothers of Italy movement, got 37 percent of the vote.
The Democratic Party won about 20 percent of the vote. None of the parties obtained a majority, which is required to form a one-party government.
READ MORE: New Italian PM Conte Backs Lifting Anti-Russia Sanctions
Among other issues, the coalition agreement between the two parties calls for the lifting of anti-Russia sanctions and for Moscow's reinstatement as a strategic mediator of the Syrian, Libyan and Yemeni crises.