There he served as Secretary General of the Hilfsverein der Deutschen Juden until his immigration to France in 1938.

In Paris from 1938 to 1940, he was a research associate of the American Jewish Joint Distribution Committee.

From 1941 to 1949, he was a research associate for the Council of Jewish Federations and Welfare Funds.

Starting in 1948, he was on the faculty of Yeshiva University as professor of Jewish history in the graduate school.

Mark Wischnitzer died on October 15, 1955, in Tel Aviv, Israel, of a heart attack.