In 1788 Pfaff became professor of mathematics in Helmstedt, and so continued until that university was abolished in 1810.
Pfaff's researches bore chiefly on the theory of series, to which he applied the methods of the so-called combinatorial school of German mathematicians, and on the solution of differential equations.
His brother, Johann Wilhelm Andreas Pfaff (1774-1835), was professor of pure and applied mathematics successively at Dorpat, Nuremberg, Wurzburg and Erlangen.
Another brother, Christian Heinrich Pfaff (1773-1852), graduated in medicine at Stuttgart in 1793, and from 1801 till his death was professor of medicine, physics and chemistry at the university of Kiel.
His Gedichte (1837), if anything, increased his reputation; his epics, Die Nibelungen inn Frack (1843) and Der Pfaff vom Kahlenberg (1850), are characterized by a fine ironic humour.