On March 3, 1948, in the midst of the Greek Civil War, he was put to trial for his political convictions and sentenced to death multiple times by the right-wing government. However, his death sentences were not executed, because of the international public outcry. His death penalties were reduced to a life sentence in 1950. Even though he was still imprisoned, Manolis Glezos was elected member of the Hellenic Parliament in 1951, under the flag of the United Democratic Left. Upon his election, he went on a hunger strike demanding the release of his fellow MPs that were imprisoned or exiled in the Greek islands. He ended his hunger strike upon the release of 7 MPs from their exile. He was released from prison on July 16, 1954.
On December 5, 1958 he was arrested again and convicted for espionage, which was common pretext for the persecution of the supporters of the left during the Cold War. The Soviet Union reacted circulating a postage stamp with Glezos, while the Greek government responded with a postage stamp depicting Imre Nagy. His release on December 15, 1962 was a result of the public outcry in Greece and abroad, including winning the Lenin Peace Prize. During his second term of post-war political imprisonment, Glezos was reelected MP with EDA in 1961. Finally, in the coup d'état of April 21, 1967, Glezos was arrested at 2 am, together with the rest of the political leaders. During the Regime of the Colonels, the military dictatorship led by George Papadopoulos, he suffered yet another four years of imprisonment and exile until his release in 1971.
Manolis Glezos' political persecution, from the Second World War to the Greek Civil War and the Regime of the Colonels totals to 11 years and 4 months of imprisonment, and 4 years and 6 months of exile.