Sezgin earned his PhD from Istanbul University under the German Orientalist Hellmut Ritter in 1950. His thesis titled "Buhari’nin Kaynakları" (The Sources of Al-Bukhari) argued that, contrary to the common belief among European orientalists, Al-Bukhari's edition of collected Hadiths was based on written sources dating back to the 7th century as well as oral history. He obtained a position at Istanbul University, but was dismissed in the wake of the 1960 coup. He moved to Germany in 1961 and started working as a visiting professor at the University of Frankfurt. He was appointed professor at the university in 1965. His research in Frankfurt focused on Islam's Golden Age of Science. In 1982, Sezgin established the Institute of the History of the Arab Islamic Sciences. Today the Institute houses the most comprehensive collection of texts on the history of Arabic-Islamic science in the world. In 1983 Sezgin also founded a unique museum within the institute, bringing together more than 800 replicas of historical scientific instruments, tools and maps, mostly belonging to the Golden Age of Islamic science. A very similar museum was opened in 2008 in Istanbul.