Middleton, a member of the National Association for the Advancement of Colored People, was actively involved in Indianapolis philanthropic and social organizations, most notably in leadership roles in YMCA.
He co-chaired the United Negro College Fund's Indiana fundraising campaign (1950–51) and was a board member of the Indianapolis Community Chest.
To earn money for medical school Middleton briefly worked as a Pullman car porter during the summer of 1919.
[3][2] Middleton briefly practiced medicine in Springfield, Tennessee, in 1928, then moved to Anderson, Indiana, where he joined the staff at Saint Johns Hospital.
[6] Middleton joined the staffs of other Indianapolis hospitals: Saint Vincent, Methodist, Community, and Winona.
[2][7] Middleton's article, "Phonocardiograph Studies on Heart Disease", published in the Journal of the National Medical Association (July 1943), is based on case histories from his work in Indianapolis.
[10] While practicing medicine in Anderson, Indiana, he served as a local Boy Scout leader and became involved with the National Negro Health Week.
In 1942, following his relocation to Indianapolis, Middleton served as the general chairman of National Negro Health Week.
[10] Middleton began serving on the Senate Avenue YMCA board in 1945 and was general chairman of its membership campaigns (1938 and 1947).
He served as president of the Senate Avenue YMCA (1951) and took a leading role in fundraising for a new branch, which opened on Fall Creek Parkway in 1959.
[7] In addition to his service to Indianapolis YMCAs, Middleton was involved with the United Negro College Fund and co-chaired its state fundraising campaign (1950–51).