In 1797 he became a Doctor of Medicine and after 1798 he became Director of the Natural Cabinet (Naturkabinetts) at the Royal Swedish Academy of Sciences in Stockholm.
Later he became a chemistry and natural history teacher at the Military Academy Karlberg, where he received in 1805 the title of professor.
[1] Quensel wrote the largest part of the text of the first four volumes of the book Svensk Botanik (1802–1843) with copper plates by Johan Wilhelm Palmstruch (1770–1811).
He also wrote the text of the first volume of Svensk Zoologi (1806–1809) and parts of Genera et species curculionidum, cum synonymia hujus familiae, specie novae aut hactenus minus cognitae, descriptionibus a dom.
Leonardo Gyllenhal, C. H. Boheman; et entomologis aliis illustratae by Carl Johan Schönherr (1772–1848).