Aged 18 he came into contact with socialist circles and met Amadeo Bordiga.
After Italy's entry in the First World War in 1915, Grieco served as a second lieutenant in the army.
He became a member of the Foreign Center of the Italian Communist Party under the pseudonym "Garlandi."
During the Second World War he worked on radio system in Moscow, where he was in charge of broadcasts for Italy.
He died of a heart attack at Massa Lombarda, during a political meeting to mark the launch of the National Farmworkers' Alliance (Alleanza nazionale dei contadini) This article about an Italian Communist Party politician is a stub.