Brett served as treasurer (appointed 1926)[3] and general manager of Macmillan Publishing.
After serving in World War II, Brett was the business manager of the New York Public Library from 1947 until 1953.
After retirement in 1953, Brett moved to Vermont, where he set up a tree farm with habitats for wildlife at Hawk's Hill in East Barnard.
Brett later donated his Hawk's Hill tree farm to the New England Forestry Foundation.
[4] Brett served in the Army Air Corps during World War II.