Noreen studied at Uppsala University and focused on Swedish dialectology in his earlier works, later shifting to the wider field of historical linguistics.
Whilst in Leipzig, Noreen was taught Lithuanian by August Leskien, a pioneer of research into sound laws.
His work, which was the first in Sweden to utilise the findings of the Neogrammarians, remained influential in the field well into the 20th century.
Noreen's academic focus in the 1880s shifted to the field of historical linguistics, primarily centred on the Germanic languages.
He proposed consistently spelling the sj-sound, voiced palatal approximant, voiceless alveolo-palatal fricative, and /ks/ (all of which continue to have several realisations in Swedish orthography) as "sj", "j", "tj", and "ks", respectively.