This paper re-examines the text of Il-khan Arghun's letter to the Pope
Nicholas IV (1290). This letter, one of the earliest surviving texts in traditional Mongolian script, is kept in the Vatican Secret Archives. Along with re-considering previous transliterations, new interpretations of certain key expressions are provided and placed within the general context of the Mongols' society and world view in the 13th century. Finally, the new version of transliteration of the letter together with its translation into both modern Khalkha Mongolian and English are suggested.