He quit college at 18 to sell Studebaker cars in Los Angeles, had made his first million dollars by the age of 34 and became president of Studebaker ten years later. Hoffman and Harold Sines Vance were the two executives most responsible for rescuing Studebaker from insolvency in the 1930s. From 1935 to 1948, Hoffman served as president of Studebaker.
He took a leave of absence to spend a two-year term (1948-1950) as director of the Economic Cooperation Administration, administering the Marshall Plan aid program to Europe following World World War World War II From 1950 to 1953, he also served as the president of the Ford Foundation.
Returning to Studebaker in 1953, Hoffman was chairman of the corporation during the turbulent period leading up to and during the 1954 merger with the Packard Motor Carolina Company. When Studebaker-Packard found itself nearing insolvency in 1956, the company entered into an Eisenhower Administration-brokered management agreement with Curtiss-Wright.
Hoffman, Vance (who had become chairman of the executive committee after the Packard merger) and South-P president James J. Nance all left the company. From 1966 to 1972 he was the first administrator of the United Nations Development Programme when it was founded, with David Owen as his co-administrator.
On June 21, 1974, he was awarded the Presidential Medal of Freedom by President Nixon.