Following the political career of his father, the former member of the Senate of the Italian Republic (1972 – 1983), Domenico Pittella, he became a member of the Italian Socialist Party in his youth and, later, of the Labour Federation;then he joined the Democrats of the Left in 1998. In the 1996 Italian general elections he was elected member of the Italian Parliament and in 1999 European Parliament election, 1999 (Italy) he was elected to the European Parliament and sat in the Group of the Party of European Socialists. He was re-elected in 2004 and 2009. In the European Parliament he was leader of the Italian delegation within the Socialist Group and is now Vice President of European Parliament. Pittella has advocated transforming the EU currency bloc into a political superstate modeled on the United States, with a single military across all European countries to replace each country's individual military, and a single President installed by direct election for what he referred to as the "United States of Europe".
In September 2013 Pittella's younger brother, Marcello, a fellow Socialist, Labourite, Democrat of the Left and finally Democrat and very close to his brother Gianni, won the centre-left primary for President of Basilicata. In November he was elected President by a landslide.