In 1895 he returned to Marburg as an associate professor, and two years later succeeded Eduard Schwartz (1858–1940) as chair of classical philology at the University of Giessen.

The two, along with Wissowa and Wilhelm Schulze, were part of a daily Tischrunde 'von glücklischter Zusammensetzung', an informal learned society of Classics scholars.

He notes that the ritual was originally Persian, brought to the West by Alexander the Great, interwoven into the worship of Isis and then seeped into the Roman sphere of influence.

Dieterich cites the works of Constantine VII Porphyrogenitus, which noted the ritual being used from Diocletian's time till the Byzantine period.

He was the author of an influential work titled "Abraxas: Studien zur Religionsgeschichte des spätern Altertums", a study based on a magical papyri that was housed at the Lateran Museum.