Hahn was born in Frankfurt am Main. In 1847, he was named Austrian consul in Ioannina, today in Greece. He was transferred to the Hellenic Kingdom on the island of Syros in 1851, and from 1869 was the consul-general in Athens. He is considered the founder of Albanian studies. He assembled and published source materials on Albanian language and culture, learned the Albanian language and demonstrated its membership in the Indo-European family of languages. He died, aged 58, in Jena.