The party took part in every government during the national liberation and constitutional periods, from June 1944 to May 1947. In the first general elections of 1948 it joined the PSI in the Democratic Popular Front but was defeated by the Christian Democracy party.
The party gained considerable electoral success during the following years and occasionally supplied external support to center-left governments, never joining directly.
In the 1970s the party moved away from Soviet obedience and marxist-leninist orthodoxy definitely embracing western democracy (eurocommunism) and sought a collaboration with Socialist and Christian Democracy parties (the historical compromise). At the time the PCI was the biggest Communist Party in a democratic state, obtaining a score of 34,4% in the 1976 general elections.
In the 1980s the party started approaching Democratic Socialism and the Socialist International.
In 1991 the PCI disbanded to form the Partito Democratico della Sinistra (PDS) or Democratic Party of the Left, with membership in the Socialist International. The communist tendency, led by Armando Cossutta, left the party to form the Partito della Rifondazione Comunista (PRC) or Communist Refoundation Party.
In 1998 the PDS, with several smaller parties, the Laburisti (liberal socialists), the Cristiano Sociali (christian socialists), the Comunisti Unitari (right-wing split of the PRC), the Sinistra Repubblicana (left republicans) and the Riformatori per l'Europa (social democratic syndicalists), co-founded the "Democratici di Sinistra" (DS) or Left Democrats party. Later in the same year the Armando Cossutta tendency left the PRC to form the Partito dei Comunisti Italiani (PdCI) or Italian Communists Party.
Party Secretaries (in chronological order):