Between 1545 and 1547, he traveled in Italy, in particular researching Latin and Greek manuscripts and studying Hebrew in Venice.
He edited the works of various authors, contributed to the Zürich Bible and published a Latin-German dictionary (Dictionarium Latinogermanicum).
In 1541, together with Peter Kolin (Petrus Cholinus), Fries translated the 1538 French dictionary (Dictionarium Latinogallicum) by Robert Estienne into German.
Later editions of Fries's dictionary did include German index; so Johann Kaspar Suicer, Joannis Frisii Dictionarium Latino-Germanicum Nec Non Germanico-Latinum (1701).
This book included 24 settings of Horatian odes for four voices in strict chordal style, the tenors of which, according to the preface, were composed by Fries, with the other parts filled in by the Zürich Cathedral organist and singer Heinrich Textor.