Prime Minister Giuseppe Conte and his ministers from the M5S and the PD raised their right hands as they took the oath in the 16th-century Quirinale presidential palace in Rome.
“We’re ready to give our utmost for the country,” M5S leader Luigi Di Maio said.
Meanwhile, PD leader Nicola Zingaretti said: “Good luck to the new government and its ministers. Let’s change Italy!”
The coalition still faces a vote in parliament, set to take place in the lower house on Monday and the upper house on Tuesday.
The new government’s first priority is the 2020 budget, which has to be submitted to parliament by the end of September, and then to Brussels by October 15.
The cabinet is the youngest ever in Italy’s post-war history – the average age being 47 years old – and has more ministers from the country’s disadvantaged south than the wealthy north.
Of the 21 ministers, nine hail from the PD, 10 from the M5S, one is a member of the small left-wing Free and Equals (LeU) party, and one has no affiliation with any political party – the new interior minister, Luciana Lamorgese.
Lamorgese is one of seven women who make up the cabinet.