Thomas Baird Appleget was born in Hightstown, New Jersey, in 1893. In 1913 Appleget enrolled at Brown University and distinguished himself as associate editor of The Brown Daily Herald and editor of the Brunonian. He was a member of Phi Beta Kappa and graduated summa cum laude.
Upon graduation in 1917 Appleget took a position as Executive Secretary to Brown University President William Faunce. In 1918 he left this position to serve as an infantryman in the U.S. Army, but following the end of World War I he returned to Brown, where he was eventually promoted to Assistant to the President and worked in the areas of public relations and student recruitment.
In 1926 Appleget became Executive Secretary to John D. Rockefeller, Jr. (JDR Jr.), who was also a Brown graduate. This position included diverse responsibilities related to the management of Rockefeller philanthropies. Appleget was also called upon for an array of special assignments, including a memorable 1926 flight with Charles Lindbergh. During a spring blizzard, Appleget was asked to accompany Lindbergh on a mission to deliver a newly developed Rockefeller Institute serum to aviator Floyd Bennett, who lay dying of pneumonia in a Quebec City hospital. Although Appleget and Lindbergh arrived safely, Bennett eventually died of his illness.
In 1929 Appleget left the service of JDR Jr. when he was appointed vice president of the Rockefeller Foundation (RF). Working out of the New York City office, Appleget led a number of initiatives with the Foundation, including the Refugee Scholars Program from 1940 to 1945.
In 1940 Appleget married Sara Elizabeth Love of North Carolina, and together they settled in Greenwich, Connecticut.
In 1949 Appleget returned again to Brown University, this time as Vice President, in which capacity he focused on public relations and fundraising.
Appleget retired from Brown University in 1959. He died of emphysema in 1982 at the age of 89.