The Nazi invasion of Greece in April 1941 caught him studying in Pogoniani and Papoulias joined the armed resistance against the Germans.

[3] He was in West Germany at the time of the 1967 coup d'état and Papoulias headed the organization of the Democratic Socialist Union Abroad, which was responsible for mobilizing Greek workers, students and scientists in Europe against the new junta of the Colonels.

[9] Papoulias was a founding member of the Panhellenic Socialist Movement (PASOK) and a close associate of its leader Andreas Papandreou.

He was also member of the Coordination Council, the Executive Bureau and the Political Secretariat, as well as Secretary of the PASOK International Relations Committee from April 1975 to 1985.

[7] During Costas Simitis' first ministerial term, he was for several years, from 1998 to 2004, president of the Permanent Committee of National Defense and Foreign Affairs.

He mediated a safe departure of trapped Palestinian militants and Yasser Arafat from Lebanon aboard Greek vessels in 1983.

[11] In his term between 1993 and 1996 and particularly at the crucial Essen Summit he played an important role in starting accession talks between the Republic of Cyprus and the European Union.

[10] As president-in-office of the European Union and member of the contact group for the former Yugoslavia he worked to bring about a resolution of the crisis in Bosnia and Herzegovina.

[22] Following the government's agreement with the International Monetary Fund on 3 May 2010, Papoulias expressed on 5 May that "our country has reached the limit of disaster" after the general strike that day turned violent and in which three bank workers were killed when the offices were set on fire by protesters.

In Thessaloniki, protesters managed to prevent the annual military parade from taking place and chanted slogans against Papoulias, calling him, among other things, a "traitor" and he was forced to leave the area.

[28] Papademos resigned few months after, in April 2012 and asked Papoulias to dissolve the Parliament and call for a snap election, scheduled for 6 May of that year.

[34] So Papopulias appointed a caretaker cabinet under Council of State president Panagiotis Pikrammenos on 16 May, and the election date set for 17 June.

[39] The murder of rapper and anti-fascist Pavlos Fyssas in September 2013 by a Golden Dawn neo-fascist sparked a wave of outrage in Greece and Papoulias stated that "it's my supreme duty as president of the republic to defend democracy and the Greek people from the storm that is approaching" and protect Greeks from neo-fascism.

[41] His presidential term ended in March 2015 and he was replaced by Prokopis Pavlopoulos, who was elected Greece's new president in a parliamentary vote in February 2015.

[44][45] His state funeral took place on 29 December at the church of Agios Spyridon in Pagrati and was attended by the country's highest authorities.