Karamanlis as early as 1958 pursued an aggressive policy toward Greek membership in the EEC.
He considered Greece's entry into the EEC a personal dream because he saw it as the fulfillment of what he called "Greece's European Destiny".
He personally lobbied European leaders, such as Germany's Konrad Adenauer and France's Charles de Gaulle followed by two years of intense negotiations with Brussels.
His intense lobbying bore fruit and on 9 July 1961 his government and the Europeans signed the protocols of Greece's Treaty of Association with the European Economic Community (EEC).
The signing ceremony in Athens was attended by top government delegations from the six-member bloc of Germany, France, Italy, Belgium, Luxemburg and the Netherlands, a precursor of the European Union.
Economy Minister Aristidis Protopapadakis and Foreign Minister Evangelos Averoff were also present.
German Vice-Chancellor Ludwig Erhard and Belgian Foreign Minister Paul-Henri Spaak, a European Union pioneer and a Karlspreis winner like Karamanlis, were among the European delegates.

This had the profound effect of ending Greece's economic isolation and breaking its political and economic dependence on US economic and military aid, mainly through NATO.
Greece became the first European country to acquire the status of associate member of the EEC outside the six nation EEC group.
In November 1962 the association treaty came into effect and envisaged the country's full membership at the EEC by 1984, after the gradual elimination of all Greek tariffs on EEC imports.
A financial protocol clause included in the treaty provided for loans to Greece subsidised by the community of about $300 million between 1962 and 1972 to help increase the competitiveness of the Greek economy in anticipation of Greece's full membership.
The Community's financial aid package as well as the protocol of accession were suspended during the 1967–74 junta years and Greece was expelled from the EEC.
As well, during the dictatorship, Greece resigned its membership in the Council of Europe fearing embarrassing investigations by the Council, following torture allegations.

Soon after returning to Greece during metapolitefsi Karamanlis reactivated his push for the country's full EEC membership in 1975 citing political and economic reasons.
Karamanlis was convinced that Greece's membership in the EEC would ensure political stability in a nation having just undergone a transition from dictatorship to Democracy.

In May 1979 he signed the full treaty of accession.
Greece became the tenth member of the EEC on 1 January 1981 three years earlier than the original protocol envisioned and despite the freezing of the treaty of accession during the junta (1967–1974).
Karamanlis as early as 1958 pursued an aggressive policy toward Greek membership in the EEC. He considered Greece's entry into the EEC a personal dream because he saw it as the fulfillment of what he called "Greece's European Destiny". He personally lobbied European leaders, such as Germany's Konrad Adenauer and France's Charles de Gaulle followed by two years of intense negotiations with Brussels. His intense lobbying bore fruit and on 9 July 1961 his government and the Europeans signed the protocols of Greece's Treaty of Association with the European Economic Community (EEC). The signing ceremony in Athens was attended by top government delegations from the six-member bloc of Germany, France, Italy, Belgium, Luxemburg and the Netherlands, a precursor of the European Union. Economy Minister Aristidis Protopapadakis and Foreign Minister Evangelos Averoff were also present. German Vice-Chancellor Ludwig Erhard and Belgian Foreign Minister Paul-Henri Spaak, a European Union pioneer and a Karlspreis winner like Karamanlis, were among the European delegates.
This had the profound effect of ending Greece's economic isolation and breaking its political and economic dependence on US economic and military aid, mainly through NATO. Greece became the first European country to acquire the status of associate member of the EEC outside the six nation EEC group. In November 1962 the association treaty came into effect and envisaged the country's full membership at the EEC by 1984, after the gradual elimination of all Greek tariffs on EEC imports. A financial protocol clause included in the treaty provided for loans to Greece subsidised by the community of about $300 million between 1962 and 1972 to help increase the competitiveness of the Greek economy in anticipation of Greece's full membership. The Community's financial aid package as well as the protocol of accession were suspended during the 1967–74 junta years and Greece was expelled from the EEC. As well, during the dictatorship, Greece resigned its membership in the Council of Europe fearing embarrassing investigations by the Council, following torture allegations.
Soon after returning to Greece during metapolitefsi Karamanlis reactivated his push for the country's full EEC membership in 1975 citing political and economic reasons. Karamanlis was convinced that Greece's membership in the EEC would ensure political stability in a nation having just undergone a transition from dictatorship to Democracy.
In May 1979 he signed the full treaty of accession. Greece became the tenth member of the EEC on 1 January 1981 three years earlier than the original protocol envisioned and despite the freezing of the treaty of accession during the junta (1967–1974).
Konstantinos Karamanlis