Njörður graduated from the University of Iceland with a Cand. mag degree in Icelandic studies in 1964, and a PhD in Norse Philology from the University of Gothenburg om 1933. He has worked as a teacher and a journalist, but entered academia as a lecturer at the University of Gothenburg in 1966. He moved to the University of Iceland in 1971, and became a full professor in 1993. He is now a professor emeritus at the University of Iceland and has worked as an author for a long time. His books have been translated into many languages.