He was ennobled in 1789 by Frederick the Great for his diplomatic service as the Prussian chargé d'affaires to the Ottoman Empire.

Upon finishing his education, he practiced as a junior lawyer in the Prussian judicial service and was appointed Clerk of the Court.

The emperor granted him his request and appointed Diez as the Prussian chargé d'affaires to the Ottoman Empire.

He was able to fund his own scientific and anthropological research, as well as a lavish lifestyle and material independence, due to his role as a benefice.

[3] In his later life he was a private scholar and free thinker, collecting books, Persian paintings, and artifacts in his villa overlooking the Spree near Berlin.