Haakon Nyhuus worked at Newberry Library under William Frederick Poole, Chief of the catalog department at the Chicago Library. He returned to Norway in 1897. From 1898, he headed the Deichman library in Kristiania (now Oslo).
He was chief editor of the six-volume encyclopedia Aschehougs Illustreret norsk Konversationsleksikon, published from 1906 to 1913.
He also introduced Dewey Decimal Classification into the library system of Norway.