The 46-year-old's candidacy was backed by the centre-left Democratic Party, of which he is a prominent member, and the centre-right People of Freedom to which he is linked by family ties, Xinhua reported.
The coalition government of the Democratic Party and the People of Freedom is composed of 21 ministers including seven women, more than ever, and the country's first non-white minister, Cecile Kyenge, who was born in the Democratic Republic of Congo.
Letta was born in Pisa. He took a degree in political science and a doctorate in European Community law before heading the youth wing of the centrist Christian Democracy Party.
In a country distinguished by its ageing political class, Letta's rise was rapid. At the age of 32, he became the youngest minister in Italy's history when he was appointed minister for community policy in 1998 in the government of then prime minister Massimo D'Alema.
He also served as industry and commerce minister till 2001.
From 2004, Letta was a member of the European Parliament until 2006, when he was appointed secretary of the council of ministers.
He is married in a second wedding to Gianna Fregonara, a journalist of Italy's largest selling newspaper Corriere della Sera. He has three children wih Fregonara.
Letta is a supporter of AC Milan, the football club owned by Berlusconi. He is also a reader of Dylan Dog, an Italian horror comics series featuring a paranormal investigator, and a music listener.
Letta has pledged to reform the parliamentary system, reduce the number of lawmakers and change an electoral law which was considered largely responsible for February's inconclusive national elections.