Lawmakers voted 378 in favour and 220 against for Renzi, the former mayor of Florence, after the Senate upper house earlier also approved a confidence vote with a far slimmer majority of 169 to 139.
Renzi, who is the European Union's youngest prime minister, earlier on Tuesday called for Italy to have a more lynchpin role in Europe in an address to lawmakers.
"Europe is not our enemy," said Renzi, who is also Italy's youngest-ever prime minister and has no experience in national government or parliament.
He said Italy's presidency of the EU in the second half of 2014 was "a gigantic opportunity".
"Europe today does not give hope because we have allowed the European debate to become about commas and percentages," he said.
"We want a Europe to which Italy does not turn just to follow a line but gives a fundamental contribution, because without Italy there is no Europe."
But he also told parliament that his first foreign trip as premier would be to Tunisia next week "and not Brussels or Berlin" because "we hope that the Mediterranean will return to centre stage".
Renzi ousted his predecessor Enrico Letta this month by engineering his dismissal by the Democratic Party that he leads and which Letta also belongs to.
Letta was in the chamber for the vote, along with Pier Luigi Bersani - a former Democratic Party leader who was widely blamed for an inconclusive result in last year's general election and was returning to parliament after suffering a brain haemorrhage last month.