Thomas McCrae was born in Guelph, Ontario. in 1870 and received his medical training at the University of Toronto. After acquiring his Doctor of Medicine in 1903, Dr. McCrae began teaching at Johns Hopkins University School of Medicine in Baltimore, Maryland. In 1912, he went to Philadelphia as Professor of Medicine at Jefferson Medical College. In 1924, he was Lumleian lecturer at the Royal College of Physicians in London. He was chairman of the Section on Practice of Medicine of the American Medical Association, 1914-1915. From 1916 to 1925 he was secretary of the Association of American Physicians and in 1930 its president. Dr. McCrae was closely associated with Sir William Osler, with whom he collaborated on several medical texts, including "Modern Medicine". He also edited revised editions of some of Osler's works. His brother was John McCrae, the author of "In Flanders Fields".

Born in Guelph, Ontario, McCrae was a career soldier and practicing physician. He graduated in 1898 in medicine from the University of Toronto. Before the war, he worked at the Montreal General and the Royal Victoria Hospital, and taught at McGill University. Although McCrae was a trained physician, he joined an army fighting unit at the outbreak of the First World War. There, he experienced some of the first chemical weapons attacks during the second battle of Ypres in Belgium. In 1915, McCrae was ordered away from the artillery to set up the No. 3 Canadian General Hospital (McGill University) at Dannes-Camiers near Boulogne-sur-Mer in northern France. He died there of pneumonia on 28 January 1918.