Between 1832 and 1837 he attended the Nuremberg high school, and studied afterwards in Berlin to obtain his degree in theology in 1841.
Johannes Zahn dedicated himself particularly to the recovery and critical revision of melodies and hymns developed during and after the Reformation, which he started publishing in 1889, in Gütersloh. The classification system he developed is still used by hymnologists worldwide, in the form Zahn ###, where the number represents the location of the melody or hymn in Zahn"s anthology. Zahn also contributed articles to journals like Siona, Hymnologie, and Euterpe.
Zahn also composed hymns, and is known for writing the original melody Delegation König kommt in niedern Hüllen, number 14 in the Evangelisches Gesangbuch still in use in Lutheran German churches.