As a much-desired appointment at the Conservatory did not materialize, Riemann went to Bromberg in 1880, but 1881–90 he was a teacher of piano and theory at Hamburg Conservatory. After a short time at the Sondershausen Conservatory, he held a post in the conservatory at Wiesbaden (1890–95), but eventually returned to Leipzig University as lecturer in 1895. In 1901, he was appointed professor.
In addition to his work as a teacher, lecturer and composer of pedagogical pieces, Riemann had a worldwide reputation as a writer on musical subjects. His best-known works are Musik-Lexikon (1882; 5th ed. 1899; Eng. trans., 1893–96), a complete dictionary of music and musicians, the Handbuch der Harmonielehre, a work on the study of harmony, and the Lehrbuch des Contrapunkts, a similar work on counterpoint, all of which have been translated into English. He was an advocate of harmonic dualism, and his theory of harmonic function is the foundation of harmonic theory as it is still taught in Germany. He also elaborated a set of harmonic transformations that was adapted by the American theorist David Lewin, and eventually evolved into a significant strain of neo-Riemannian theory. Another pillar of modern neo-Riemannian theory, the Tonnetz, was not Riemann's own invention, but he played an important role in popularizing and disseminating it.
He authored many works on many different branches of music. His pupils included the German composer, pianist, organist, and conductor Max Reger, and the musicologist and composer Walter Niemann.