While ambassador to Turkey, Steinhardt, particularly because he was Jewish, was involved in the rescue of Hungarian Jews from Bergen Belsen. He also played a significant role in helping many eminent intellectuals fleeing Europe to find refuge in Turkey.
In 1945, President Truman appointed Steinhardt ambassador to Czechoslovakia, and to Canada in 1948. While serving as the Ambassador to Canada, he was killed in a plane crash on 28 March 1950 near Ramsayville in Ontario, while en route to Washington, D. C. He is buried in Arlington National Cemetery.