The pushing forward of the negotiating process to this end was a goal of decisive importance for Karamanlis after the restoration of democracy in July 1974. The events that had intervened after Greece had become an Associate Member, both domestically and on a broader international scale, had confirmed the importance of the country's full membership of the EEC. This would consolidate its democratic institutions, safeguard its security and ensure its economic development and social modernisation, and also strengthen its diplomatic position and international reputation.

 With this conviction, Karamanlis officially submitted the Greek application on 12th June 1975 and, despite the initially negative response of the Commission, in February 1976, after his powerful personal intervention, it was adopted by the EEC Council of Ministers. The success of the long discussions, which focused particularly on the length and terms of the transitional period, and their avoidance of issues that had nothing to do with the specific request to join, would require repeated and drastic interventions on the part of the Greek Prime Minister in order to secure the advocacy of the political leaders of the nine European partners at the most crucial stages of the negotiations. After the final agreement was reached in December 1978, the Treaty of Accession was signed at a celebratory ceremony at the Zappeion Hall, and Greece became a full member of the European Economic Community on 1st January 1981.