Schiff retained many of his Orthodox habits (he said his prayers every morning) but was affiliated with New York’s Temple Emanu-FJ and the Reform Movement. He was active in the establishment and development of the Jewish Theological Seminary, and also supported both Ycshiva College and Hebrew Union College. He used his personal wealth and influence on behalf of Jews everywhere, and his widespread philanthropic and communal activities brought him recognition as the foremost figure of American Jewry. He was a leading supporter of the Jewish Publication Society of America and financed its publication of the Schiff Library of Jewish Classics.
Jacob Schiff was a founding member of the American Jewish Committee and in 1914 was instrumental in creating the American Jewish Relief Committee, which later became the Joint Distribution Committee.