In 1965, he emigrated to West Germany, where he initially worked at the Bonn Rhenanian State Museum from 1965 to 1968.
Alföldy was appointed professor for Ancient History at the University of Heidelberg in 1975 and stayed there until his retirement in 2002.
Within the scope of his epigraphical studies, Gezá Alföldy visited many countries (Albania, Algeria, Austria, Britain, Cyprus, Egypt, France, Greece, Hungary, Italy, Jordan, Libya, Portugal, Spain, Syria, Turkey, Tunisia, and Yugoslavia) in order to research original ancient inscriptions.
Furthermore, Alföldy was a guest professor at the Institute for Advanced Study, Princeton (1972/73), in Rome from 1986 and 2003, in Paris (1991), and Pécs (still in 1993) in Poznań (1992), in Budapest (1993), and also in Barcelona in 1997 and 1998.
His name was especially associated with the Heidelberger Althistorische Beiträge und Epigraphische Studien (HABES), which he was sole editor from 1986.