A warm admirer of Klopstock, Denis was one of the leading members of the group of so-called bards; and his original poetry, published under the title Die Lieder Sineds des Barden (1772), shows all the extravagances of the bardic movement.

[1] More important than either Denis' original poetry or his translations were his efforts to familiarise the Austrians with the literature of Northern Germany; his Sammlung kürzerer Gedichte aus den neuern Dichtern Deutschlandes, 3 volumes (1762–1766), was in this respect invaluable.

[1] Ossians und Sineds Lieder have not been reprinted since 1791; but a selection of Denis' poetry, edited by Richard Hamel, is to found in volume 48 (1884) of Kürschners Deutsche Nationalliteratur.

His Literarischer Nachlass was published by Joseph Friedrich Freiherr von Retzer in 1802 (2 volumes),[1] two years after Denis had died in Vienna, aged 71.

In addition to his literary output, working with Ignaz Schiffermüller, Denis formed an early collection of butterflies and moths, and published the first catalogue of the Lepidoptera found around Vienna.