Jaretzki helped draft the Investment Company Act of 1940 passed by the United States Congress.
He later acted as an adviser to the U.S. Delegation at the Évian Conference for Jewish refugees fleeing Nazi persecution.
He served as vice chairman of AJJDC and chaired their Committee on Refugee Aid in Central and South America.
Jaretzki served as a member of the Council on Foreign Relations and as an honorary trustee of the Public Education Association of New York City.
He also served as president of St. John's Guild, an agency that assisted ill children and older adults, from 1958 to 1961.