The object of the authors’ interest is a source which has been unknown to Polish medieval studies, namely „The book of miracles of St. Bernardino of Siena” written by Conradus of Freystadt. It is housed in the collection of the French National Library in Paris (MS nr NAL 1763). The authors analyzed the so-called „Polish part” of the aforementioned book, containing notes about the miracles which took place at the intercession of St. Bernardino during the visit of his disciple John of Capistrano in the Kingdom of Poland during the years 1453-1454. Additionaly, the genesis and the first phase of the development of St. Bernardino’s cult in Poland are discussed. The edition of the „Polish part” of this Liber miraculorum („Book of miracles”) is appended to the article.