In 1884 he took the same position at the University of Freiburg, but returned to Leipzig in 1887 as successor to Georg Curtius; for the rest of his professional life (until 1919), Brugmann was professor of Sanskrit and comparative linguistics there.

As well as in laying stress on the observation of phonetic laws and their operation, it emphasized the working of analogy as an important linguistic factor in modern languages.

Brugmann's fame rests on the two volumes on phonology, morphology, and word formation which he contributed to the five-volume Grundriss der vergleichenden Grammatik der indogermanischen Sprachen ("Outline of the Comparative Grammar of the Indo-Germanic Languages"), published from 1886 to 1893.

This totally empirical presentation multiplies the time necessary to follow Brugmann's argument, but makes the effort all the more fruitful.

In addition, Brugmann stayed in touch closely with the scholars who were revolutionizing Indo-European linguistics for the daughter languages, in particular Bartholomae for Old Iranian, Hübschmann for Armenian, and Rudolf Thurneysen for Old Irish.

Brugmann was knighted by the King of Saxony, and in 1896 he was invited to attend the jubilee of Princeton University, where he received the degree of doctor of laws.