Hoornbeck was a writer of polemical works. His many works include
De Conversione Indorum et Gentilum, libri duo (on the conversion of native populations of Asia and America)
Pro Convincendis, et Convertendis Judaeis, libri octo (on the conversion of the Jews)
He attacked the Socinians, Mennonites, the Remonstrants and Cartesians. A collection of his polemical writing was the Summa Controversiarum Religionis; Cum Infidelibus, Hæreticis, Schismaticis: Id Est, Gentilibus, Judæis, Muhammedanis; Papistis, Anabaptistis, Enthusiastis et Libertinis, Socinianis; Remonstrantibus, Lutheranis, Brouvnistis, Græcis of 1653.