When St. Paul was on his second missionary journey in 52-53, with Silas and Timothy, while he was at Troas in Mysia he had the vision "Pass over into Macedonia, and help us" that brought him for the first time to Europe, and at Philippi in Macedonia he founded the first Christian Church on European soil. From there he came to Thessalonica and Berea and, travelling southwards, to Athens. There he preached about "the unknown God " on the Areopagus, and went on to Corinth. At Corinth he was brought before Gallio, proconsul of Achaia; from Cenchrae, the port of Corinth, he sailed back to Ephesus with Priscilla and Aquila . On his third journey (54-58) he came again to Macedonia (about the year 57 ), thence "to Greece" and stayed for three months in Corinth before going back to Asia Minor (Troas) via Macedonia). In all these places St. Paul preached, according to his custom, first to the colonies of Jews and then to Gentiles.
The alleged missions of other Apostles to Greece rest on a less firm footing. St. Andrew is said to have preached in Scythia, Thrace, Epirus, Macedonia and Achaia, and to have been crucified (on a cross of the shape to which he has given his name) at Patras, by order of the Proconsul Aegeas. The story of his mission and martyrdom is as old as the second century.
The Church spread rapidly in Greece. We hear of bishops in various cities during the persecution.