Grandson of Zevi Hirsch Chajes a well known rabbinic scholar, and nephew of Isaac Chajes, rabbi of Brody, Galicia (now in the Ukraine). Perez Chajes was born in Brody where he received education from his father and uncle both in Jewish studies (Talmud) as well as in general studies. At a later age he studied at the Jewish Theological Seminary in Vienna and at the University of Vienna. He was teacher of religion in Lemberg (now Lviv, in the Ukraine), teacher of Jewish history and Bible at the Collegio Rabbinico Italiano in Florence, Italy; teacher of Hebrew at the University of Florence (1904), rabbi of Trieste (1912), where he founded a Jewish periodical and was his only contributor. During his activity in Italy, Perez Chajes was the champion of the Italian Zionist movement and contributed in writing to the Zionist ideas (he was a favourite of the movement from his youth).
In 1918 he returned to Vienna where he became Deputy Chief Rabbi, and shortly thereafter Chief Rabbi of Vienna. This post he held for nine years till his death (1927). Rabbi Perez Chajes was the foremost spiritual leader in Jewish Austria. In his work with the Jewish Community he helped the Jews who suffered during WWI, both in Trieste and in Vienna and continued to do so during the depression years after the WW1. He was very interested in Jewish education and founded two Jewish elementary schools and one high school (which was named after him following his death). He was also involved in other projects and also taught Biblical Studies at the Hebrew Paedagogium. As a Zionist leader Perez Chajes attended the San Remo Peace Conference (1920), where he was elected chairman of the Actions Committee(1921-1925).
His Zionist views were not accepted by the wealthy assimilationists, and his liberal and Zionist attitude towards religion were not accepted by the Orthodox Jews. However, his ideas were very much accepted by the youth. Perez Chajes was very charismatic and an exellent orator.