After the civil wars, led by the Communist Guerrillas from December 1944 until October 1949, the Greek government received financial support by the U.S. with the Marshall Plan. By 1951, Greece was already a member of the United Nations (UN) and became a member of the North Atlantic Treaty Organization (NATO). In April 1967, a military junta, led by George Papadopoulos, took control over Greece and deposed King Constantine II. But in 1973, a coup was conducted to oust Papadopoulos.

In December 1974, months after the military rule, a referendum was passed in Greece which put an end to the monarchy and confirmed Greece a republic. The first civilian government of Greece since 1967 was formed by Karamanlis, who turned back from exile and became the premier.

On January 1, 1981, Greece officially became the 10th member of the European Union (EU). From 1981 to 1989, Greece had its first Socialist government, led by the premier George Papandreou, who was also the creator and leader of the Panhellenic Socialist Movement (PASOK).

Greece and Turkey continued arguments between each other, including disputes about a 10-acre isolated island and about Cyprus, which is still divided into Turkish and Greek parts. Between 1996 and 2004, the government of Greece was led by the pro-Western Socialist Kostas Simitis, who was expected to recover the Greek economy.

In the beginning of the 21st Century, the Greek government succeeded to capture and neutralise the leftist terrorist organisation, which eluded Greek authorities for 27 years and was responsible for more than 20 murders of businessmen and diplomats. In March 2004, elections in Greece saw the conservative New Democracy Party win against PASOK, and Kostas Karamanlis became the new prime minister, who successfully organised the Olympic Games in Greece.

In late August 2007, more than 220 fires threatened to destroy ancient Olympic sites around Athens. More than 60 people died and some 500,000 acres lands were destroyed by the fires. Karamanlis was criticised for not having to control the fires, but in September he and his New Democracy Party were re-elected, again over the PASOK party.