Thomas Cunningham Penfold was born on 14 October 1872 in Brampton, Cumberland. He was the son of John Blake Penfold, a painter, and Marianne Penfold (formerly Cunningham) and twin brother of Henry Penfold. Penfold studied at Edinburgh University, graduating M.B., C.M. in 1894. He then went on to study for his M.R.C.S., L.R.C.P. (London) and the D.T.H. (Dublin), and then set himself up in private medical practice at Benwell, Newcastle. He was joined by another brother, Dr. W. J. Penfold who later became Director of the Baker Institute, Melbourne, Australia.

After several years in practice Penfold began to follow up an interest in public health work, and in 1910 he was appointed as Medical Officer to the Isolation Hospital, Prudhoe, and was also Medical Officer in Hexham. In 1914 he became Medical Officer of Health to the Bishop Auckland Rural District Council and in 1925 he moved to Chester-le-Street as Medical Officer of Health and Medical Officer of the Chester-le-Street Isolation Hospital. While in post he was involved in the moves towards slum clearance in the rural area of Chester-le-Street and he also campaigned for the creation of healthy schools and healthy homes for children so that infectious diseases could be reduced.

Dr. Thomas Cunningham Penfold died suddenly in a Newcastle nursing home on 13 May 1935, leaving a widow and three daughters.